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doc/lvol: add description for clear-method when creating lvol bdevs

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Change-Id: I93647d2633f88522e3c0826eb7a379b9cfa0126d
Signed-off-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Reviewed-on: https://review.gerrithub.io/c/442563
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
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Tomasz Zawadzki 2019-01-29 05:23:26 -05:00 committed by Ben Walker
parent 80a9ef4042
commit 0c0d9d4e0a
2 changed files with 6 additions and 1 deletions
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3
CHANGELOG.md
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@ -90,6 +90,9 @@ planned shutdown.
Logical volume bdev can now be marked as read only using `set_read_only_lvol_bdev` RPC.
This allows for basing clones on top of lvol_bdev without first creating a snapshot.
Added option to change method for data erasure when deleting lvol or resizing down.
Default of unmapping clusters can now be changed to writing zeroes or no operation.
### log
"trace flags" are now referred to as "log flags" in the SPDK log API. The

4
doc/lvol.md
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@ -27,6 +27,7 @@ Representation of an SPDK block device (spdk_bdev) with an lvol implementation.
A logical volume block device translates generic SPDK block device I/O (spdk_bdev_io) operations into the equivalent SPDK blob operations. Combination of lvol name and lvolstore name gives lvol_bdev alias name in a form "lvs_name/lvol_name". block_size of the created bdev is always 4096, due to blobstore page size. Cluster_size is configurable by parameter.
Size of the new bdev will be rounded up to nearest multiple of cluster_size.
By default lvol bdevs claim part of lvol store equal to their set size. When thin provision option is enabled, no space is taken from lvol store until data is written to lvol bdev.
By default when deleting lvol bdev or resizing down, allocated clusters are unmapped. Optional --clear-method parameter can be passed on creation to change that behavior to writing zeroes or performing no operation.
## Thin provisioning {#lvol_thin_provisioning}
@ -105,13 +106,14 @@ rename_lvol_store [-h] old_name new_name
RPC regarding lvol and spdk bdev:
```
construct_lvol_bdev [-h] [-u UUID] [-l LVS_NAME] [-t] lvol_name size
construct_lvol_bdev [-h] [-u UUID] [-l LVS_NAME] [-t] [-c CLEAR_METHOD] lvol_name size
Creates lvol with specified size and name on lvolstore specified by its uuid
or name. Then constructs spdk bdev on top of that lvol and presents it as spdk bdev.
User may use -t switch to create thin provisioned lvol.
Returns the name of new spdk bdev
optional arguments:
-h, --help show help
-c, --clear-method specify data clusters clear method "none", "unmap" (default), "write_zeroes"
get_bdevs [-h] [-b NAME]
User can view created bdevs using this call including those created on top of lvols.
optional arguments: