54 lines
2.0 KiB
ReStructuredText
54 lines
2.0 KiB
ReStructuredText
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Storage concepts
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================
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The OpenStack stack uses the following storage types:
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.. list-table:: Storage types
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:header-rows: 1
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:widths: 30 30 30
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* - On-instance / ephemeral
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- Block storage (cinder)
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- Object Storage (swift)
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* - Runs operating systems and provides scratch space
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- Used for adding additional persistent storage to a virtual machine (VM)
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- Used for storing virtual machine images and data
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* - Persists until VM is terminated
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- Persists until deleted
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- Persists until deleted
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* - Access associated with a VM
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- Access associated with a VM
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- Available from anywhere
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* - Implemented as a filesystem underlying OpenStack Compute
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- Mounted via OpenStack Block Storage controlled protocol (for example, iSCSI)
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- REST API
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* - Encryption is available
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- Encryption is available
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- Work in progress - expected for the Mitaka release
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* - Administrator configures size setting, based on flavors
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- Sizings based on need
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- Easily scalable for future growth
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* - Example: 10 GB first disk, 30 GB/core second disk
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- Example: 1 TB "extra hard drive"
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- Example: 10s of TBs of data set storage
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.. note::
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- *You cannot use OpenStack Object Storage like a traditional hard
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drive.* The Object Storage relaxes some of the constraints of a
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POSIX-style file system to get other gains. You can access the
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objects through an API which uses HTTP. Subsequently you don't have
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to provide atomic operations (that is, relying on eventual
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consistency), you can scale a storage system easily and avoid a
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central point of failure.
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- *The OpenStack Image service is used to manage the virtual machine
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images in an OpenStack cluster, not store them.* It provides an
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abstraction to different methods for storage - a bridge to the
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storage, not the storage itself.
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- *The OpenStack Object Storage can function on its own.* The Object
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Storage (swift) product can be used independently of the Compute
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(nova) product.
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