451 lines
21 KiB
ReStructuredText
451 lines
21 KiB
ReStructuredText
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================
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Deployment Guide
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================
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-----------------------
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Hardware Considerations
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-----------------------
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Swift is designed to run on commodity hardware. At Rackspace, our storage
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servers are currently running fairly generic 4U servers with 24 2T SATA
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drives and 8 cores of processing power. RAID on the storage drives is not
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required and not recommended. Swift's disk usage pattern is the worst
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case possible for RAID, and performance degrades very quickly using RAID 5
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or 6.
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------------------
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Deployment Options
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------------------
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The swift services run completely autonomously, which provides for a lot of
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flexibility when architecting the hardware deployment for swift. The 4 main
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services are:
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#. Proxy Services
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#. Object Services
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#. Container Services
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#. Account Services
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The Proxy Services are more CPU and network I/O intensive. If you are using
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10g networking to the proxy, or are terminating SSL traffic at the proxy,
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greater CPU power will be required.
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The Object, Container, and Account Services (Storage Services) are more disk
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and network I/O intensive.
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The easiest deployment is to install all services on each server. There is
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nothing wrong with doing this, as it scales each service out horizontally.
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At Rackspace, we put the Proxy Services on their own servers and all of the
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Storage Services on the same server. This allows us to send 10g networking to
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the proxy and 1g to the storage servers, and keep load balancing to the
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proxies more manageable. Storage Services scale out horizontally as storage
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servers are added, and we can scale overall API throughput by adding more
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Proxies.
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If you need more throughput to either Account or Container Services, they may
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each be deployed to their own servers. For example you might use faster (but
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more expensive) SAS or even SSD drives to get faster disk I/O to the databases.
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Load balancing and network design is left as an excercise to the reader,
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but this is a very important part of the cluster, so time should be spent
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designing the network for a Swift cluster.
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------------------
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Preparing the Ring
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------------------
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The first step is to determine the number of partitions that will be in the
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ring. We recommend that there be a minimum of 100 partitions per drive to
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insure even distribution accross the drives. A good starting point might be
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to figure out the maximum number of drives the cluster will contain, and then
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multiply by 100, and then round up to the nearest power of two.
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For example, imagine we are building a cluster that will have no more than
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5,000 drives. That would mean that we would have a total number of 500,000
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partitions, which is pretty close to 2^19, rounded up.
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It is also a good idea to keep the number of partitions small (realatively).
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The more partitions there are, the more work that has to be done by the
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replicators and other backend jobs and the more memory the rings consume in
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process. The goal is to find a good balance between small rings and maximum
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cluster size.
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The next step is to determine the number of replicas to store of the data.
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Currently it is recommended to use 3 (as this is the only value that has
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been tested). The higher the number, the more storage that is used but the
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less likely you are to lose data.
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It is also important to determine how many zones the cluster should have. It is
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recommended to start with a minimum of 5 zones. You can start with fewer, but
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our testing has shown that having at least five zones is optimal when failures
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occur. We also recommend trying to configure the zones as high a level as
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possible to create as much isolation as possible. Some example things to take
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into consideration can include physical location, power availability, and
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network connectivity. For example, in a small cluster you might decide to
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split the zones up by cabinet, with each cabinet having its own power and
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network connectivity. The zone concept is very abstract, so feel free to use
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it in whatever way best isolates your data from failure. Zones are referenced
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by number, beginning with 1.
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You can now start building the ring with::
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swift-ring_builder <builder_file> create <part_power> <replicas> <min_part_hours>
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This will start the ring build process creating the <builder_file> with
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2^<part_power> partitions. <min_part_hours> is the time in hours before a
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specific partition can be moved in succession (24 is a good value for this).
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Devices can be added to the ring with::
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swift-ring_builder <builder_file> add z<zone>-<ip>:<port>/<device_name>_<meta> <weight>
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This will add a device to the ring where <builder_file> is the name of the
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builder file that was created previously, <zone> is the number of the zone
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this device is in, <ip> is the ip address of the server the device is in,
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<port> is the port number that the server is running on, <device_name> is
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the name of the device on the server (for example: sdb1), <meta> is a string
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of metadata for the device (optional), and <weight> is a float weight that
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determines how many partitions are put on the device relative to the rest of
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the devices in the cluster (a good starting point is 100.0 x TB on the drive).
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Add each device that will be initially in the cluster.
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Once all of the devices are added to the ring, run::
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swift_ring_builder <builder_file> rebalance
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This will distribute the partitions across the drives in the ring. It is
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important whenever making changes to the ring to make all the changes
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required before running rebalance. This will ensure that the ring stays as
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balanced as possible, and as few partitions are moved as possible.
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The above process should be done to make a ring for each storage serivce
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(Account, Container and Object). The builder files will be needed in future
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changes to the ring, so it is very important that these be kept and backed up.
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The resulting .tar.gz ring file should be pushed to all of the servers in the
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cluster. For more information about building rings, running
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swift_ring_builder with no options will display help text with available
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commands and options. More information on how the ring works internally
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can be found in the :doc:`Ring Overview <overview_ring>`.
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---------------------------
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Object Server Configuration
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---------------------------
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An Example Object Server configuration can be found at
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etc/object-server.conf-sample in the source code repository.
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The following configuration options are available:
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[object-server]
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================== ========== =============================================
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Option Default Description
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------------------ ---------- ---------------------------------------------
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swift_dir /etc/swift Swift configuration directory
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devices /srv/node Parent directory of where devices are mounted
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mount_check true Weather or not check if the devices are
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mounted to prevent accidently writing
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to the root device
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bind_ip 0.0.0.0 IP Address for server to bind to
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bind_port 6000 Port for server to bind to
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workers 1 Number of workers to fork
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log_facility LOG_LOCAL0 Syslog log facility
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log_level INFO Logging level
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log_requests True Weather or not to log each request
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user swift User to run as
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node_timeout 3 Request timeout to external services
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conn_timeout 0.5 Connection timeout to external services
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network_chunk_size 65536 Size of chunks to read/write over the
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network
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disk_chunk_size 65536 Size of chunks to read/write to disk
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max_upload_time 86400 Maximum time allowed to upload an object
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slow 0 If > 0, Minimum time in seconds for a PUT
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or DELETE request to complete
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================== ========== =============================================
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[object-replicator]
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================== ========== ===========================================
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Option Default Description
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------------------ ---------- -------------------------------------------
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log_facility LOG_LOCAL0 Syslog log facility
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log_level INFO Logging level
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daemonize yes Weather or not to run replication as a
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daemon
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run_pause 30 Time in seconds to wait between replication
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passes
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concurrency 1 Number of replication workers to spawn
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timeout 5 Timeout value sent to rsync --timeout and
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--contimeout options
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stats_interval 3600 Interval in seconds between logging
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replication statistics
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reclaim_age 604800 Time elapsed in seconds before an object
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can be reclaimed
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================== ========== ===========================================
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[object-updater]
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================== ========== ===========================================
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Option Default Description
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------------------ ---------- -------------------------------------------
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log_facility LOG_LOCAL0 Syslog log facility
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log_level INFO Logging level
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interval 300 Minimum time for a pass to take
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concurrency 1 Number of updater workers to spawn
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node_timeout 10 Request timeout to external services
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conn_timeout 0.5 Connection timeout to external services
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slowdown 0.01 Time in seconds to wait between objects
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================== ========== ===========================================
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[object-auditor]
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================== ========== ===========================================
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Option Default Description
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------------------ ---------- -------------------------------------------
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log_facility LOG_LOCAL0 Syslog log facility
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log_level INFO Logging level
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interval 1800 Minimum time for a pass to take
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node_timeout 10 Request timeout to external services
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conn_timeout 0.5 Connection timeout to external services
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================== ========== ===========================================
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------------------------------
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Container Server Configuration
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------------------------------
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An example Container Server configuration can be found at
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etc/container-server.conf-sample in the source code repository.
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The following configuration options are available:
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[container-server]
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================== ========== ============================================
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Option Default Description
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------------------ ---------- --------------------------------------------
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log_facility LOG_LOCAL0 Syslog log facility
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log_level INFO Logging level
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swift_dir /etc/swift Swift configuration directory
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devices /srv/node Parent irectory of where devices are mounted
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mount_check true Weather or not check if the devices are
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mounted to prevent accidently writing
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to the root device
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bind_ip 0.0.0.0 IP Address for server to bind to
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bind_port 6001 Port for server to bind to
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workers 1 Number of workers to fork
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user swift User to run as
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node_timeout 3 Request timeout to external services
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conn_timeout 0.5 Connection timeout to external services
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================== ========== ============================================
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[container-replicator]
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================== ========== ===========================================
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Option Default Description
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------------------ ---------- -------------------------------------------
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log_facility LOG_LOCAL0 Syslog log facility
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log_level INFO Logging level
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per_diff 1000
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concurrency 8 Number of replication workers to spawn
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run_pause 30 Time in seconds to wait between replication
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passes
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node_timeout 10 Request timeout to external services
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conn_timeout 0.5 Connection timeout to external services
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reclaim_age 604800 Time elapsed in seconds before a container
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can be reclaimed
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================== ========== ===========================================
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[container-updater]
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================== ========== ===========================================
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Option Default Description
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------------------ ---------- -------------------------------------------
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log_facility LOG_LOCAL0 Syslog log facility
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log_level INFO Logging level
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interval 300 Minimum time for a pass to take
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concurrency 4 Number of updater workers to spawn
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node_timeout 3 Request timeout to external services
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conn_timeout 0.5 Connection timeout to external services
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slowdown 0.01 Time in seconds to wait between containers
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================== ========== ===========================================
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[container-auditor]
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================== ========== ===========================================
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Option Default Description
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------------------ ---------- -------------------------------------------
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log_facility LOG_LOCAL0 Syslog log facility
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log_level INFO Logging level
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interval 1800 Minimum time for a pass to take
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node_timeout 10 Request timeout to external services
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conn_timeout 0.5 Connection timeout to external services
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================== ========== ===========================================
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----------------------------
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Account Server Configuration
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----------------------------
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An example Account Server configuration can be found at
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etc/account-server.conf-sample in the source code repository.
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The following configuration options are available:
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[account-server]
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================== ========== =============================================
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Option Default Description
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------------------ ---------- ---------------------------------------------
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log_facility LOG_LOCAL0 Syslog log facility
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log_level INFO Logging level
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swift_dir /etc/swift Swift configuration directory
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devices /srv/node Parent directory or where devices are mounted
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mount_check true Weather or not check if the devices are
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mounted to prevent accidently writing
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|
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to the root device
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bind_ip 0.0.0.0 IP Address for server to bind to
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bind_port 6002 Port for server to bind to
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workers 1 Number of workers to fork
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user swift User to run as
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================== ========== =============================================
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[account-replicator]
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================== ========== ===========================================
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Option Default Description
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------------------ ---------- -------------------------------------------
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log_facility LOG_LOCAL0 Syslog log facility
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log_level INFO Logging level
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per_diff 1000
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concurrency 8 Number of replication workers to spawn
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run_pause 30 Time in seconds to wait between replication
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passes
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node_timeout 10 Request timeout to external services
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conn_timeout 0.5 Connection timeout to external services
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reclaim_age 604800 Time elapsed in seconds before a account
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can be reclaimed
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================== ========== ===========================================
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[account-auditor]
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==================== ========== ===========================================
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Option Default Description
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-------------------- ---------- -------------------------------------------
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log_facility LOG_LOCAL0 Syslog log facility
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log_level INFO Logging level
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interval 1800 Minimum time for a pass to take
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max_container_count 100 Maximum containers randomly picked for
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a given account audit
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node_timeout 10 Request timeout to external services
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conn_timeout 0.5 Connection timeout to external services
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==================== ========== ===========================================
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[account-reaper]
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================== ========== ===========================================
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Option Default Description
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------------------ ---------- -------------------------------------------
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log_facility LOG_LOCAL0 Syslog log facility
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log_level INFO Logging level
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concurrency 25 Number of replication workers to spawn
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interval 3600 Minimum time for a pass to take
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node_timeout 10 Request timeout to external services
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conn_timeout 0.5 Connection timeout to external services
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================== ========== ===========================================
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----------------------
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General Service Tuning
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----------------------
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|
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Most services support either a worker or concurrency value in the settings.
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This allows the services to make effective use of the cores available. A good
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starting point to set the concurrency level for the proxy and storage services
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|
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to 2 times the number of cores available. If more than one service is
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sharing a server, then some experimentaiton may be needed to find the best
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balance.
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|
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|
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At Rackspace, our Proxy servers have dual quad core processors, giving us 8
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cores. Our testing has shown 16 workers to be a pretty good balance when
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saturating a 10g network and gives good CPU utilization.
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|
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Our Storage servers all run together on the same servers. These servers have
|
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|
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dual quad core processors, for 8 cores total. We run the Account, Container,
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|
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and Object servers with 8 workers each. Most of the background jobs are run
|
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|
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at a concurrency of 1, with the exception of the replicators which are run at
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a concurrency of 2.
|
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|
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The above configuration setting should be taken as suggestions and testing
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||
|
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of configuration settings should be done to ensure best utilization of CPU,
|
||
|
|
network connectivity, and disk I/O.
|
||
|
|
|
||
|
|
-------------------------
|
||
|
|
Filesystem Considerations
|
||
|
|
-------------------------
|
||
|
|
|
||
|
|
Swift is designed to be mostly filesystem agnostic--the only requirement
|
||
|
|
beeing that the filesystem supports extended attributes (xattrs). After
|
||
|
|
thorough testing with our use cases and hardware configurations, XFS was
|
||
|
|
the best all-around choice. If you decide to use a filesystem other than
|
||
|
|
XFS, we highly recommend thorough testing.
|
||
|
|
|
||
|
|
If you are using XFS, some settings that can dramatically impact
|
||
|
|
performance. We recommend the following when creating the XFS
|
||
|
|
partition::
|
||
|
|
|
||
|
|
mkfs.xfs -i size=1024 -f /dev/sda1
|
||
|
|
|
||
|
|
Setting the inode size is important, as XFS stores xattr data in the inode.
|
||
|
|
If the metadata is too large to fit in the inode, a new extent is created,
|
||
|
|
which can cause quite a performance problem. Upping the inode size to 1024
|
||
|
|
bytes provides enough room to write the default metadata, plus a little
|
||
|
|
headroom. We do not recommend running Swift on RAID, but if you are using
|
||
|
|
RAID it is also important to make sure that the proper sunit and swidth
|
||
|
|
settings get set so that XFS can make most efficient use of the RAID array.
|
||
|
|
|
||
|
|
We also recommend the following example mount options when using XFS::
|
||
|
|
|
||
|
|
mount -t xfs -o noatime,nodiratime,nobarrier,logbufs=8 /dev/sda1 /srv/node/sda
|
||
|
|
|
||
|
|
For a standard swift install, all data drives are mounted directly under
|
||
|
|
/srv/node (as can be seen in the above example of mounting /def/sda1 as
|
||
|
|
/srv/node/sda). If you choose to mount the drives in another directory,
|
||
|
|
be sure to set the `devices` config option in all of the server configs to
|
||
|
|
point to the correct directory.
|
||
|
|
|
||
|
|
---------------------
|
||
|
|
General System Tuning
|
||
|
|
---------------------
|
||
|
|
|
||
|
|
Rackspace currently runs Swift on Ubuntu Server 10.04, and the following
|
||
|
|
changes have been found to be useful for our use cases.
|
||
|
|
|
||
|
|
The following settings should be in `/etc/sysctl.conf`::
|
||
|
|
|
||
|
|
# disable TIME_WAIT.. wait..
|
||
|
|
net.ipv4.tcp_tw_recycle=1
|
||
|
|
net.ipv4.tcp_tw_reuse=1
|
||
|
|
|
||
|
|
# disable syn cookies
|
||
|
|
net.ipv4.tcp_syncookies = 0
|
||
|
|
|
||
|
|
# double amount of allowed conntrack
|
||
|
|
net.ipv4.netfilter.ip_conntrack_max = 262144
|
||
|
|
|
||
|
|
To load the updated sysctl settings, run ``sudo sysctl -p``
|
||
|
|
|
||
|
|
A note about changing the TIME_WAIT values. By default the OS will hold
|
||
|
|
a port open for 60 seconds to ensure that any remaining packets can be
|
||
|
|
received. During high usage, and with the number of connections that are
|
||
|
|
created, it is easy to run out of ports. We can change this since we are
|
||
|
|
in control of the network. If you are not in control of the network, or
|
||
|
|
do not expect high loads, then you may not want to adjust those values.
|
||
|
|
|
||
|
|
----------------------
|
||
|
|
Logging Considerations
|
||
|
|
----------------------
|
||
|
|
|
||
|
|
Swift is set up to log directly to syslog. Every service can be configured
|
||
|
|
with the `log_facility` option to set the syslog log facility destination.
|
||
|
|
It is recommended to use syslog-ng to route the logs to specific log
|
||
|
|
files locally on the server and also to remote log collecting servers.
|