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liberasurecode
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==============
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liberasurecode is an Erasure Code API library written in C with pluggable Erasure Code backends.
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----
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Highlights
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==========
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* Unified Erasure Coding interface for common storage workloads.
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* Pluggable Erasure Code backends - As of v1.0-rc1, liberasurecode supports the following backends:
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- 'Jerasure' - Erasure Coding library that supports Reed-Solomon, Cauchy backends [1]
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- 'ISA-L' - Intel Storage Acceleration Library - SIMD accelerated Erasure Coding backends [2]
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- 'SHSS' - NTT Lab Japan's hybrid Erasure Coding backend [4]
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- 'Flat XOR HD' - built-in to liberasurecode, based on [3]
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- 'NULL' template backend implemented to help future backend writers
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* True 'plugin' architecture - liberasurecode uses Dynamically Loaded (DL) libraries to realize a true 'plugin' architecture. This also allows one to build liberasurecode indepdendent of the Erasure Code backend libraries.
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* Cross-platform - liberasurecode is known to work on Linux (Fedora/Debian flavors), Solaris, BSD and Darwin/Mac OS X.
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* Community support - Developed alongside Erasure Code authority Kevin Greenan, liberasurecode is an actively maintained open-source project with growing community involvement (Openstack Swift, Ceph, PyECLib).
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----
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License
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==========
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liberasurecode is distributed under the terms of the **BSD** license.
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----
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Active Users
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====================
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* PyECLib - Python EC library: https://pypi.python.org/pypi/PyECLib
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* Openstack Swift Object Store - https://wiki.openstack.org/wiki/Swift
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----
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liberasurecode API Definition
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=============================
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----
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Backend Support
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---------------
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``` c
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typedef enum {
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EC_BACKEND_NULL = 0, /* "null" */
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EC_BACKEND_JERASURE_RS_VAND = 1, /* "jerasure_rs_vand" */
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EC_BACKEND_JERASURE_RS_CAUCHY = 2, /* "jerasure_rs_cauchy" */
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EC_BACKEND_FLAT_XOR_HD = 3, /* "flat_xor_hd */
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EC_BACKEND_ISA_L_RS_VAND = 4, /* "isa_l_rs_vand */
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EC_BACKENDS_MAX,
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} ec_backend_id_t;
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```
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----
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User Arguments
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--------------
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``` c
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/**
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* Common and backend-specific args
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* to be passed to liberasurecode_instance_create()
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*/
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struct ec_args {
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int k; /* number of data fragments */
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int m; /* number of parity fragments */
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int w; /* word size, in bits (optional) */
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int hd; /* hamming distance (=m for Reed-Solomon) */
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union {
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struct {
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uint64_t arg1; /* sample arg */
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} null_args; /* args specific to the null codes */
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struct {
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uint64_t x, y; /* reserved for future expansion */
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uint64_t z, a; /* reserved for future expansion */
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} reserved;
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} priv_args1;
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void *priv_args2; /** flexible placeholder for
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* future backend args */
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ec_checksum_type_t ct; /* fragment checksum type */
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};
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```
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---
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User-facing API Functions
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-------------------------
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``` c
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/* liberasurecode frontend API functions */
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/**
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* Create a liberasurecode instance and return a descriptor
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* for use with EC operations (encode, decode, reconstruct)
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*
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* @param id - one of the supported backends as
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* defined by ec_backend_id_t
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* @param ec_args - arguments to the EC backend
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* arguments common to all backends
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* k - number of data fragments
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* m - number of parity fragments
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* w - word size, in bits
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* hd - hamming distance (=m for Reed-Solomon)
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* ct - fragment checksum type (stored with the fragment metadata)
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* backend-specific arguments
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* null_args - arguments for the null backend
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* flat_xor_hd, jerasure do not require any special args
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*
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* @return liberasurecode instance descriptor (int > 0)
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*/
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int liberasurecode_instance_create(const ec_backend_id_t id,
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struct ec_args *args);
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/**
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* Close a liberasurecode instance
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*
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* @param desc - liberasurecode descriptor to close
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*
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* @return 0 on success, otherwise non-zero error code
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*/
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int liberasurecode_instance_destroy(int desc);
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/**
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* Erasure encode a data buffer
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*
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* @param desc - liberasurecode descriptor/handle
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* from liberasurecode_instance_create()
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* @param orig_data - data to encode
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* @param orig_data_size - length of data to encode
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* @param encoded_data - pointer to _output_ array (char **) of k data
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* fragments (char *), allocated by the callee
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* @param encoded_parity - pointer to _output_ array (char **) of m parity
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* fragments (char *), allocated by the callee
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* @param fragment_len - pointer to _output_ length of each fragment, assuming
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* all fragments are the same length
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*
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* @return 0 on success, -error code otherwise
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*/
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int liberasurecode_encode(int desc,
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const char *orig_data, uint64_t orig_data_size, /* input */
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char ***encoded_data, char ***encoded_parity, /* output */
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uint64_t *fragment_len); /* output */
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/**
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* Cleanup structures allocated by librasurecode_encode
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*
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* The caller has no context, so cannot safely free memory
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* allocated by liberasurecode, so it must pass the
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* deallocation responsibility back to liberasurecode.
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*
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* @param desc - liberasurecode descriptor/handle
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* from liberasurecode_instance_create()
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* @param encoded_data - (char **) array of k data
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* fragments (char *), allocated by liberasurecode_encode
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* @param encoded_parity - (char **) array of m parity
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* fragments (char *), allocated by liberasurecode_encode
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*
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* @return 0 in success; -error otherwise
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*/
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int liberasurecode_encode_cleanup(int desc, char **encoded_data,
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char **encoded_parity);
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/**
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* Reconstruct original data from a set of k encoded fragments
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*
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* @param desc - liberasurecode descriptor/handle
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* from liberasurecode_instance_create()
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* @param fragments - erasure encoded fragments (> = k)
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* @param num_fragments - number of fragments being passed in
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* @param fragment_len - length of each fragment (assume they are the same)
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* @param force_metadata_checks - force fragment metadata checks (default: 0)
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* @param out_data - _output_ pointer to decoded data
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* @param out_data_len - _output_ length of decoded output
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*
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* @return 0 on success, -error code otherwise
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*/
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int liberasurecode_decode(int desc,
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char **available_fragments, /* input */
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int num_fragments, uint64_t fragment_len, /* input */
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int force_metadata_checks, /* input */
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char **out_data, uint64_t *out_data_len); /* output */
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/**
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* Cleanup structures allocated by librasurecode_decode
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*
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* The caller has no context, so cannot safely free memory
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* allocated by liberasurecode, so it must pass the
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* deallocation responsibility back to liberasurecode.
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*
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* @param desc - liberasurecode descriptor/handle
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* from liberasurecode_instance_create()
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* @param data - (char *) buffer of data decoded by librasurecode_decode
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*
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* @return 0 on success; -error otherwise
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*/
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int liberasurecode_decode_cleanup(int desc, char *data);
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/**
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* Reconstruct a missing fragment from a subset of available fragments
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*
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* @param desc - liberasurecode descriptor/handle
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* from liberasurecode_instance_create()
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* @param available_fragments - erasure encoded fragments
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* @param num_fragments - number of fragments being passed in
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* @param fragment_len - size in bytes of the fragments
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* @param destination_idx - missing idx to reconstruct
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* @param out_fragment - output of reconstruct
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*
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* @return 0 on success, -error code otherwise
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*/
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int liberasurecode_reconstruct_fragment(int desc,
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char **available_fragments, /* input */
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int num_fragments, uint64_t fragment_len, /* input */
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int destination_idx, /* input */
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char* out_fragment); /* output */
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/**
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* Return a list of lists with valid rebuild indexes given
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* a list of missing indexes.
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*
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* @desc: liberasurecode instance descriptor (obtained with
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* liberasurecode_instance_create)
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* @fragments_to_reconstruct list of indexes to reconstruct
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* @fragments_to_exclude list of indexes to exclude from
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* reconstruction equation
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* @fragments_needed list of fragments needed to reconstruct
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* fragments in fragments_to_reconstruct
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*
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* @return 0 on success, non-zero on error
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*/
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int liberasurecode_fragments_needed(int desc,
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int *fragments_to_reconstruct,
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int *fragments_to_exclude,
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int *fragments_needed);
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```
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Erasure Code Fragment Checksum Types Supported
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----------------------------------------------
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``` c
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/* Checksum types supported for fragment metadata stored in each fragment */
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typedef enum {
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CHKSUM_NONE = 0, /* "none" (default) */
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CHKSUM_CRC32 = 1, /* "crc32" */
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CHKSUM_MD5 = 2, /* "md5" */
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CHKSUM_TYPES_MAX,
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} ec_checksum_type_t;
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```
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Erasure Code Fragment Checksum API
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----------------------------------
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``` c
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struct
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fragment_metadata
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{
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uint32_t idx; /* 4 */
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uint32_t size; /* 4 */
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uint64_t orig_data_size; /* 8 */
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uint8_t chksum_type; /* 1 */
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uint32_t chksum[LIBERASURECODE_MAX_CHECKSUM_LEN]; /* 16 */
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uint8_t chksum_mismatch; /* 1 */
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} fragment_metadata_t;
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/**
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* Get opaque metadata for a fragment. The metadata is opaque to the
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* client, but meaningful to the underlying library. It is used to verify
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* stripes in verify_stripe_metadata().
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*
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* @param desc - liberasurecode descriptor/handle
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* from liberasurecode_instance_create()
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* @param fragment - fragment data pointer
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* @param fragment_metadata - pointer to allocated buffer of size at least
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* sizeof(struct fragment_metadata) to hold fragment metadata struct
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*
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* @return 0 on success, non-zero on error
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*/
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int liberasurecode_get_fragment_metadata(int desc,
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char *fragment, fragment_metadata_t *fragment_metadata);
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/**
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* Verify a subset of fragments generated by encode()
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*
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* @param desc - liberasurecode descriptor/handle
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* from liberasurecode_instance_create()
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* @param fragments - fragments part of the EC stripe to verify
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* @param num_fragments - number of fragments part of the EC stripe
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*
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* @return 1 if stripe checksum verification is successful, 0 otherwise
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*/
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int liberasurecode_verify_stripe_metadata(int desc,
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char **fragments, int num_fragments);
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/**
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* This computes the aligned size of a buffer passed into
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* the encode function. The encode function must pad fragments
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* to be algined with the word size (w) and the last fragment also
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* needs to be aligned. This computes the sum of the algined fragment
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* sizes for a given buffer to encode.
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*
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* @param desc - liberasurecode descriptor/handle
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* from liberasurecode_instance_create()
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* @param data_len - original data length in bytes
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*
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* @return aligned length, or -error code on error
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*/
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int liberasurecode_get_aligned_data_size(int desc, uint64_t data_len);
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/**
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* This will return the minimum encode size, which is the minimum
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* buffer size that can be encoded.
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*
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* @param desc - liberasurecode descriptor/handle
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* from liberasurecode_instance_create()
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*
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* @return minimum data length length, or -error code on error
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*/
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int liberasurecode_get_minimum_encode_size(int desc);
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||||
```
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||||
----
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Error Codes
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||||
-----------
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||||
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||||
``` c
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/* Error codes */
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typedef enum {
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EBACKENDNOTSUPP = 200, /* EC Backend not supported by the library */
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EECMETHODNOTIMPL = 201, /* EC Backend method not implemented */
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EBACKENDINITERR = 202, /* EC Backend could not be initialized */
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EBACKENDINUSE = 203, /* EC Backend in use (locked) */
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} LIBERASURECODE_ERROR_CODES;
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||||
```
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||||
---
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||||
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Build and Install
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||||
=================
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||||
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||||
To build the liberasurecode repository, perform the following from the
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top-level directory:
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||||
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``` sh
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$ ./autogen.sh
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$ ./configure
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||||
$ make
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||||
$ make test
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||||
$ sudo make install
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||||
```
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||||
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||||
----
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||||
Code organization
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=================
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```
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|-- include
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| +-- erasurecode
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| | +-- erasurecode.h --> liberasurecode frontend API header
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| | +-- erasurecode_backend.h --> liberasurecode backend API header
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||||
| +-- xor_codes --> headers for the built-in XOR codes
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||||
|
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||||
|-- src
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| |-- erasurecode.c --> liberasurecode API implementation
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||||
| | (frontend + backend)
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| |-- backends
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| | +-- null
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| | +--- null.c --> 'null' erasure code backend (template backend)
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| | +-- xor
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| | +--- flat_xor_hd.c --> 'flat_xor_hd' erasure code backend (built-in)
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||||
| | +-- jerasure
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| | +-- jerasure_rs_cauchy.c --> 'jerasure_rs_vand' erasure code backend (jerasure.org)
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||||
| | +-- jerasure_rs_vand.c --> 'jerasure_rs_cauchy' erasure code backend (jerasure.org)
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||||
| | +-- isa-l
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| | +-- isa_l_rs_vand.c --> 'isa_l_rs_vand' erasure code backend (Intel)
|
||||
| | +-- shss
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||||
| | +-- shss.c --> 'shss' erasure code backend (NTT Labs)
|
||||
| |
|
||||
| |-- builtin
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||||
| | +-- xor_codes --> XOR HD code backend, built-in erasure
|
||||
| | | code implementation (shared library)
|
||||
| | +-- xor_code.c
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||||
| | +-- xor_hd_code.c
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||||
| |
|
||||
| +-- utils
|
||||
| +-- chksum --> fragment checksum utils for erasure
|
||||
| +-- alg_sig.c coded fragments
|
||||
| +-- crc32.c
|
||||
|
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||||
|-- doc --> API Documentation
|
||||
| +-- Doxyfile
|
||||
| +-- html
|
||||
|
|
||||
|--- test --> Test routines
|
||||
| +-- builtin
|
||||
| | +-- xor_codes
|
||||
| +-- liberasurecode_test.c
|
||||
| +-- utils
|
||||
|
|
||||
|-- autogen.sh
|
||||
|-- configure.ac
|
||||
|-- Makefile.am
|
||||
|-- README
|
||||
|-- NEWS
|
||||
|-- COPYING
|
||||
|-- AUTHORS
|
||||
|-- INSTALL
|
||||
+-- ChangeLog
|
||||
```
|
||||
---
|
||||
|
||||
References
|
||||
==========
|
||||
|
||||
[1] Jerasure, C library that supports erasure coding in storage applications, http://jerasure.org
|
||||
|
||||
[2] Intel(R) Storage Acceleration Library (Open Source Version), https://01.org/intel%C2%AE-storage-acceleration-library-open-source-version
|
||||
|
||||
[3] Greenan, Kevin M et al, "Flat XOR-based erasure codes in storage systems", http://www.kaymgee.com/Kevin_Greenan/Publications_files/greenan-msst10.pdf
|
||||
|
||||
[4] Kota Tsuyuzaki <tsuyuzaki.kota@lab.ntt.co.jp>, Ryuta Kon <kon.ryuta@po.ntts.co.jp>, "NTT SHSS Erasure Coding backend"
|
||||
|
||||
liberasurecode
|
||||
==============
|
||||
|
||||
liberasurecode is an Erasure Code API library written in C with pluggable Erasure Code backends.
|
||||
|
||||
----
|
||||
|
||||
Highlights
|
||||
==========
|
||||
|
||||
* Unified Erasure Coding interface for common storage workloads.
|
||||
|
||||
* Pluggable Erasure Code backends - As of v1.0-rc1, liberasurecode supports the following backends:
|
||||
|
||||
- 'Jerasure' - Erasure Coding library that supports Reed-Solomon, Cauchy backends [1]
|
||||
- 'ISA-L' - Intel Storage Acceleration Library - SIMD accelerated Erasure Coding backends [2]
|
||||
- 'SHSS' - NTT Lab Japan's hybrid Erasure Coding backend [4]
|
||||
- 'Flat XOR HD' - built-in to liberasurecode, based on [3]
|
||||
- 'NULL' template backend implemented to help future backend writers
|
||||
|
||||
|
||||
* True 'plugin' architecture - liberasurecode uses Dynamically Loaded (DL) libraries to realize a true 'plugin' architecture. This also allows one to build liberasurecode indepdendent of the Erasure Code backend libraries.
|
||||
|
||||
* Cross-platform - liberasurecode is known to work on Linux (Fedora/Debian flavors), Solaris, BSD and Darwin/Mac OS X.
|
||||
|
||||
* Community support - Developed alongside Erasure Code authority Kevin Greenan, liberasurecode is an actively maintained open-source project with growing community involvement (Openstack Swift, Ceph, PyECLib).
|
||||
|
||||
----
|
||||
|
||||
License
|
||||
==========
|
||||
|
||||
liberasurecode is distributed under the terms of the **BSD** license.
|
||||
|
||||
----
|
||||
|
||||
Active Users
|
||||
====================
|
||||
|
||||
* PyECLib - Python EC library: https://pypi.python.org/pypi/PyECLib
|
||||
* Openstack Swift Object Store - https://wiki.openstack.org/wiki/Swift
|
||||
|
||||
----
|
||||
|
||||
liberasurecode API Definition
|
||||
=============================
|
||||
----
|
||||
|
||||
Backend Support
|
||||
---------------
|
||||
|
||||
``` c
|
||||
|
||||
typedef enum {
|
||||
EC_BACKEND_NULL = 0, /* "null" */
|
||||
EC_BACKEND_JERASURE_RS_VAND = 1, /* "jerasure_rs_vand" */
|
||||
EC_BACKEND_JERASURE_RS_CAUCHY = 2, /* "jerasure_rs_cauchy" */
|
||||
EC_BACKEND_FLAT_XOR_HD = 3, /* "flat_xor_hd */
|
||||
EC_BACKEND_ISA_L_RS_VAND = 4, /* "isa_l_rs_vand */
|
||||
EC_BACKENDS_MAX,
|
||||
} ec_backend_id_t;
|
||||
|
||||
```
|
||||
|
||||
----
|
||||
|
||||
User Arguments
|
||||
--------------
|
||||
|
||||
``` c
|
||||
|
||||
/**
|
||||
* Common and backend-specific args
|
||||
* to be passed to liberasurecode_instance_create()
|
||||
*/
|
||||
struct ec_args {
|
||||
int k; /* number of data fragments */
|
||||
int m; /* number of parity fragments */
|
||||
int w; /* word size, in bits (optional) */
|
||||
int hd; /* hamming distance (=m for Reed-Solomon) */
|
||||
|
||||
union {
|
||||
struct {
|
||||
uint64_t arg1; /* sample arg */
|
||||
} null_args; /* args specific to the null codes */
|
||||
struct {
|
||||
uint64_t x, y; /* reserved for future expansion */
|
||||
uint64_t z, a; /* reserved for future expansion */
|
||||
} reserved;
|
||||
} priv_args1;
|
||||
|
||||
void *priv_args2; /** flexible placeholder for
|
||||
* future backend args */
|
||||
ec_checksum_type_t ct; /* fragment checksum type */
|
||||
};
|
||||
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
User-facing API Functions
|
||||
-------------------------
|
||||
|
||||
``` c
|
||||
|
||||
/* liberasurecode frontend API functions */
|
||||
|
||||
/**
|
||||
* Create a liberasurecode instance and return a descriptor
|
||||
* for use with EC operations (encode, decode, reconstruct)
|
||||
*
|
||||
* @param id - one of the supported backends as
|
||||
* defined by ec_backend_id_t
|
||||
* @param ec_args - arguments to the EC backend
|
||||
* arguments common to all backends
|
||||
* k - number of data fragments
|
||||
* m - number of parity fragments
|
||||
* w - word size, in bits
|
||||
* hd - hamming distance (=m for Reed-Solomon)
|
||||
* ct - fragment checksum type (stored with the fragment metadata)
|
||||
* backend-specific arguments
|
||||
* null_args - arguments for the null backend
|
||||
* flat_xor_hd, jerasure do not require any special args
|
||||
*
|
||||
* @return liberasurecode instance descriptor (int > 0)
|
||||
*/
|
||||
int liberasurecode_instance_create(const ec_backend_id_t id,
|
||||
struct ec_args *args);
|
||||
|
||||
/**
|
||||
* Close a liberasurecode instance
|
||||
*
|
||||
* @param desc - liberasurecode descriptor to close
|
||||
*
|
||||
* @return 0 on success, otherwise non-zero error code
|
||||
*/
|
||||
int liberasurecode_instance_destroy(int desc);
|
||||
|
||||
|
||||
/**
|
||||
* Erasure encode a data buffer
|
||||
*
|
||||
* @param desc - liberasurecode descriptor/handle
|
||||
* from liberasurecode_instance_create()
|
||||
* @param orig_data - data to encode
|
||||
* @param orig_data_size - length of data to encode
|
||||
* @param encoded_data - pointer to _output_ array (char **) of k data
|
||||
* fragments (char *), allocated by the callee
|
||||
* @param encoded_parity - pointer to _output_ array (char **) of m parity
|
||||
* fragments (char *), allocated by the callee
|
||||
* @param fragment_len - pointer to _output_ length of each fragment, assuming
|
||||
* all fragments are the same length
|
||||
*
|
||||
* @return 0 on success, -error code otherwise
|
||||
*/
|
||||
int liberasurecode_encode(int desc,
|
||||
const char *orig_data, uint64_t orig_data_size, /* input */
|
||||
char ***encoded_data, char ***encoded_parity, /* output */
|
||||
uint64_t *fragment_len); /* output */
|
||||
|
||||
/**
|
||||
* Cleanup structures allocated by librasurecode_encode
|
||||
*
|
||||
* The caller has no context, so cannot safely free memory
|
||||
* allocated by liberasurecode, so it must pass the
|
||||
* deallocation responsibility back to liberasurecode.
|
||||
*
|
||||
* @param desc - liberasurecode descriptor/handle
|
||||
* from liberasurecode_instance_create()
|
||||
* @param encoded_data - (char **) array of k data
|
||||
* fragments (char *), allocated by liberasurecode_encode
|
||||
* @param encoded_parity - (char **) array of m parity
|
||||
* fragments (char *), allocated by liberasurecode_encode
|
||||
*
|
||||
* @return 0 in success; -error otherwise
|
||||
*/
|
||||
int liberasurecode_encode_cleanup(int desc, char **encoded_data,
|
||||
char **encoded_parity);
|
||||
|
||||
/**
|
||||
* Reconstruct original data from a set of k encoded fragments
|
||||
*
|
||||
* @param desc - liberasurecode descriptor/handle
|
||||
* from liberasurecode_instance_create()
|
||||
* @param fragments - erasure encoded fragments (> = k)
|
||||
* @param num_fragments - number of fragments being passed in
|
||||
* @param fragment_len - length of each fragment (assume they are the same)
|
||||
* @param force_metadata_checks - force fragment metadata checks (default: 0)
|
||||
* @param out_data - _output_ pointer to decoded data
|
||||
* @param out_data_len - _output_ length of decoded output
|
||||
*
|
||||
* @return 0 on success, -error code otherwise
|
||||
*/
|
||||
int liberasurecode_decode(int desc,
|
||||
char **available_fragments, /* input */
|
||||
int num_fragments, uint64_t fragment_len, /* input */
|
||||
int force_metadata_checks, /* input */
|
||||
char **out_data, uint64_t *out_data_len); /* output */
|
||||
|
||||
/**
|
||||
* Cleanup structures allocated by librasurecode_decode
|
||||
*
|
||||
* The caller has no context, so cannot safely free memory
|
||||
* allocated by liberasurecode, so it must pass the
|
||||
* deallocation responsibility back to liberasurecode.
|
||||
*
|
||||
* @param desc - liberasurecode descriptor/handle
|
||||
* from liberasurecode_instance_create()
|
||||
* @param data - (char *) buffer of data decoded by librasurecode_decode
|
||||
*
|
||||
* @return 0 on success; -error otherwise
|
||||
*/
|
||||
int liberasurecode_decode_cleanup(int desc, char *data);
|
||||
|
||||
/**
|
||||
* Reconstruct a missing fragment from a subset of available fragments
|
||||
*
|
||||
* @param desc - liberasurecode descriptor/handle
|
||||
* from liberasurecode_instance_create()
|
||||
* @param available_fragments - erasure encoded fragments
|
||||
* @param num_fragments - number of fragments being passed in
|
||||
* @param fragment_len - size in bytes of the fragments
|
||||
* @param destination_idx - missing idx to reconstruct
|
||||
* @param out_fragment - output of reconstruct
|
||||
*
|
||||
* @return 0 on success, -error code otherwise
|
||||
*/
|
||||
int liberasurecode_reconstruct_fragment(int desc,
|
||||
char **available_fragments, /* input */
|
||||
int num_fragments, uint64_t fragment_len, /* input */
|
||||
int destination_idx, /* input */
|
||||
char* out_fragment); /* output */
|
||||
|
||||
/**
|
||||
* Return a list of lists with valid rebuild indexes given
|
||||
* a list of missing indexes.
|
||||
*
|
||||
* @desc: liberasurecode instance descriptor (obtained with
|
||||
* liberasurecode_instance_create)
|
||||
* @fragments_to_reconstruct list of indexes to reconstruct
|
||||
* @fragments_to_exclude list of indexes to exclude from
|
||||
* reconstruction equation
|
||||
* @fragments_needed list of fragments needed to reconstruct
|
||||
* fragments in fragments_to_reconstruct
|
||||
*
|
||||
* @return 0 on success, non-zero on error
|
||||
*/
|
||||
int liberasurecode_fragments_needed(int desc,
|
||||
int *fragments_to_reconstruct,
|
||||
int *fragments_to_exclude,
|
||||
int *fragments_needed);
|
||||
|
||||
```
|
||||
|
||||
Erasure Code Fragment Checksum Types Supported
|
||||
----------------------------------------------
|
||||
|
||||
``` c
|
||||
|
||||
/* Checksum types supported for fragment metadata stored in each fragment */
|
||||
typedef enum {
|
||||
CHKSUM_NONE = 0, /* "none" (default) */
|
||||
CHKSUM_CRC32 = 1, /* "crc32" */
|
||||
CHKSUM_MD5 = 2, /* "md5" */
|
||||
CHKSUM_TYPES_MAX,
|
||||
} ec_checksum_type_t;
|
||||
|
||||
```
|
||||
|
||||
Erasure Code Fragment Checksum API
|
||||
----------------------------------
|
||||
|
||||
``` c
|
||||
|
||||
struct
|
||||
fragment_metadata
|
||||
{
|
||||
uint32_t idx; /* 4 */
|
||||
uint32_t size; /* 4 */
|
||||
uint64_t orig_data_size; /* 8 */
|
||||
uint8_t chksum_type; /* 1 */
|
||||
uint32_t chksum[LIBERASURECODE_MAX_CHECKSUM_LEN]; /* 16 */
|
||||
uint8_t chksum_mismatch; /* 1 */
|
||||
} fragment_metadata_t;
|
||||
|
||||
|
||||
/**
|
||||
* Get opaque metadata for a fragment. The metadata is opaque to the
|
||||
* client, but meaningful to the underlying library. It is used to verify
|
||||
* stripes in verify_stripe_metadata().
|
||||
*
|
||||
* @param desc - liberasurecode descriptor/handle
|
||||
* from liberasurecode_instance_create()
|
||||
* @param fragment - fragment data pointer
|
||||
* @param fragment_metadata - pointer to allocated buffer of size at least
|
||||
* sizeof(struct fragment_metadata) to hold fragment metadata struct
|
||||
*
|
||||
* @return 0 on success, non-zero on error
|
||||
*/
|
||||
int liberasurecode_get_fragment_metadata(int desc,
|
||||
char *fragment, fragment_metadata_t *fragment_metadata);
|
||||
|
||||
/**
|
||||
* Verify a subset of fragments generated by encode()
|
||||
*
|
||||
* @param desc - liberasurecode descriptor/handle
|
||||
* from liberasurecode_instance_create()
|
||||
* @param fragments - fragments part of the EC stripe to verify
|
||||
* @param num_fragments - number of fragments part of the EC stripe
|
||||
*
|
||||
* @return 1 if stripe checksum verification is successful, 0 otherwise
|
||||
*/
|
||||
int liberasurecode_verify_stripe_metadata(int desc,
|
||||
char **fragments, int num_fragments);
|
||||
|
||||
/**
|
||||
* This computes the aligned size of a buffer passed into
|
||||
* the encode function. The encode function must pad fragments
|
||||
* to be algined with the word size (w) and the last fragment also
|
||||
* needs to be aligned. This computes the sum of the algined fragment
|
||||
* sizes for a given buffer to encode.
|
||||
*
|
||||
* @param desc - liberasurecode descriptor/handle
|
||||
* from liberasurecode_instance_create()
|
||||
* @param data_len - original data length in bytes
|
||||
*
|
||||
* @return aligned length, or -error code on error
|
||||
*/
|
||||
int liberasurecode_get_aligned_data_size(int desc, uint64_t data_len);
|
||||
|
||||
/**
|
||||
* This will return the minimum encode size, which is the minimum
|
||||
* buffer size that can be encoded.
|
||||
*
|
||||
* @param desc - liberasurecode descriptor/handle
|
||||
* from liberasurecode_instance_create()
|
||||
*
|
||||
* @return minimum data length length, or -error code on error
|
||||
*/
|
||||
int liberasurecode_get_minimum_encode_size(int desc);
|
||||
|
||||
```
|
||||
----
|
||||
|
||||
Error Codes
|
||||
-----------
|
||||
|
||||
``` c
|
||||
|
||||
/* Error codes */
|
||||
typedef enum {
|
||||
EBACKENDNOTSUPP = 200, /* EC Backend not supported by the library */
|
||||
EECMETHODNOTIMPL = 201, /* EC Backend method not implemented */
|
||||
EBACKENDINITERR = 202, /* EC Backend could not be initialized */
|
||||
EBACKENDINUSE = 203, /* EC Backend in use (locked) */
|
||||
} LIBERASURECODE_ERROR_CODES;
|
||||
|
||||
```
|
||||
---
|
||||
|
||||
Build and Install
|
||||
=================
|
||||
|
||||
To build the liberasurecode repository, perform the following from the
|
||||
top-level directory:
|
||||
|
||||
``` sh
|
||||
$ ./autogen.sh
|
||||
$ ./configure
|
||||
$ make
|
||||
$ make test
|
||||
$ sudo make install
|
||||
```
|
||||
|
||||
----
|
||||
|
||||
Code organization
|
||||
=================
|
||||
```
|
||||
|-- include
|
||||
| +-- erasurecode
|
||||
| | +-- erasurecode.h --> liberasurecode frontend API header
|
||||
| | +-- erasurecode_backend.h --> liberasurecode backend API header
|
||||
| +-- xor_codes --> headers for the built-in XOR codes
|
||||
|
|
||||
|-- src
|
||||
| |-- erasurecode.c --> liberasurecode API implementation
|
||||
| | (frontend + backend)
|
||||
| |-- backends
|
||||
| | +-- null
|
||||
| | +--- null.c --> 'null' erasure code backend (template backend)
|
||||
| | +-- xor
|
||||
| | +--- flat_xor_hd.c --> 'flat_xor_hd' erasure code backend (built-in)
|
||||
| | +-- jerasure
|
||||
| | +-- jerasure_rs_cauchy.c --> 'jerasure_rs_vand' erasure code backend (jerasure.org)
|
||||
| | +-- jerasure_rs_vand.c --> 'jerasure_rs_cauchy' erasure code backend (jerasure.org)
|
||||
| | +-- isa-l
|
||||
| | +-- isa_l_rs_vand.c --> 'isa_l_rs_vand' erasure code backend (Intel)
|
||||
| | +-- shss
|
||||
| | +-- shss.c --> 'shss' erasure code backend (NTT Labs)
|
||||
| |
|
||||
| |-- builtin
|
||||
| | +-- xor_codes --> XOR HD code backend, built-in erasure
|
||||
| | | code implementation (shared library)
|
||||
| | +-- xor_code.c
|
||||
| | +-- xor_hd_code.c
|
||||
| |
|
||||
| +-- utils
|
||||
| +-- chksum --> fragment checksum utils for erasure
|
||||
| +-- alg_sig.c coded fragments
|
||||
| +-- crc32.c
|
||||
|
|
||||
|-- doc --> API Documentation
|
||||
| +-- Doxyfile
|
||||
| +-- html
|
||||
|
|
||||
|--- test --> Test routines
|
||||
| +-- builtin
|
||||
| | +-- xor_codes
|
||||
| +-- liberasurecode_test.c
|
||||
| +-- utils
|
||||
|
|
||||
|-- autogen.sh
|
||||
|-- configure.ac
|
||||
|-- Makefile.am
|
||||
|-- README
|
||||
|-- NEWS
|
||||
|-- COPYING
|
||||
|-- AUTHORS
|
||||
|-- INSTALL
|
||||
+-- ChangeLog
|
||||
```
|
||||
---
|
||||
|
||||
References
|
||||
==========
|
||||
|
||||
[1] Jerasure, C library that supports erasure coding in storage applications, http://jerasure.org
|
||||
|
||||
[2] Intel(R) Storage Acceleration Library (Open Source Version), https://01.org/intel%C2%AE-storage-acceleration-library-open-source-version
|
||||
|
||||
[3] Greenan, Kevin M et al, "Flat XOR-based erasure codes in storage systems", http://www.kaymgee.com/Kevin_Greenan/Publications_files/greenan-msst10.pdf
|
||||
|
||||
[4] Kota Tsuyuzaki <tsuyuzaki.kota@lab.ntt.co.jp>, Ryuta Kon <kon.ryuta@po.ntts.co.jp>, "NTT SHSS Erasure Coding backend"
|
Loading…
Reference in New Issue
Block a user