doc: Minor updates to bdev user guide
Signed-off-by: Monica Kenguva <monica.kenguva@intel.com> Change-Id: I28047e71535046b898fa14bfb210ec4019614554 Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/3465 Community-CI: Mellanox Build Bot Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com> Reviewed-by: Ben Walker <benjamin.walker@intel.com> Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
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Monica Kenguva
Tomasz Zawadzki
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doc/bdev.md
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doc/bdev.md
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# Block Device User Guide {#bdev}
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# Block Device User Guide {#bdev}
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# Target Audience {#bdev_ug_targetaudience}
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This user guide is intended for software developers who have knowledge of block storage, storage drivers, issuing JSON-RPC commands and storage services such as RAID, compression, crypto, and others.
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# Introduction {#bdev_ug_introduction}
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# Introduction {#bdev_ug_introduction}
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The SPDK block device layer, often simply called *bdev*, is a C library
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The SPDK block device layer, often simply called *bdev*, is a C library
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@ -35,72 +39,12 @@ directly from SPDK application by running `scripts/rpc.py rpc_get_methods`.
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Detailed help for each command can be displayed by adding `-h` flag as a
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Detailed help for each command can be displayed by adding `-h` flag as a
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command parameter.
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command parameter.
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# General Purpose RPCs {#bdev_ug_general_rpcs}
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# Configuring Block Device Modules {#bdev_ug_general_rpcs}
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## bdev_get_bdevs {#bdev_ug_get_bdevs}
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Block devices can be configured using JSON RPCs. A complete list of available RPC commands
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with detailed information can be found on the @ref jsonrpc_components_bdev page.
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List of currently available block devices including detailed information about
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# Common Block Device Configuration Examples
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them can be get by using `bdev_get_bdevs` RPC command. User can add optional
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parameter `name` to get details about specified by that name bdev.
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Example response
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~~~
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{
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"num_blocks": 32768,
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"assigned_rate_limits": {
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"rw_ios_per_sec": 10000,
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"rw_mbytes_per_sec": 20
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},
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"supported_io_types": {
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"reset": true,
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"nvme_admin": false,
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"unmap": true,
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"read": true,
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"write_zeroes": true,
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"write": true,
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"flush": true,
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"nvme_io": false
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},
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"driver_specific": {},
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"claimed": false,
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"block_size": 4096,
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"product_name": "Malloc disk",
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"name": "Malloc0"
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}
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~~~
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## bdev_set_qos_limit {#bdev_set_qos_limit}
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Users can use the `bdev_set_qos_limit` RPC command to enable, adjust, and disable
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rate limits on an existing bdev. Two types of rate limits are supported:
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IOPS and bandwidth. The rate limits can be enabled, adjusted, and disabled at any
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time for the specified bdev. The bdev name is a required parameter for this
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RPC command and at least one of `rw_ios_per_sec` and `rw_mbytes_per_sec` must be
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specified. When both rate limits are enabled, the first met limit will
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take effect. The value 0 may be specified to disable the corresponding rate
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limit. Users can run this command with `-h` or `--help` for more information.
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## Histograms {#rpc_bdev_histogram}
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The `bdev_enable_histogram` RPC command allows to enable or disable gathering
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latency data for specified bdev. Histogram can be downloaded by the user by
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calling `bdev_get_histogram` and parsed using scripts/histogram.py script.
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Example command
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`rpc.py bdev_enable_histogram Nvme0n1 --enable`
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The command will enable gathering data for histogram on Nvme0n1 device.
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`rpc.py bdev_get_histogram Nvme0n1 | histogram.py`
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The command will download gathered histogram data. The script will parse
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the data and show table containing IO count for latency ranges.
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`rpc.py bdev_enable_histogram Nvme0n1 --disable`
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The command will disable histogram on Nvme0n1 device.
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# Ceph RBD {#bdev_config_rbd}
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# Ceph RBD {#bdev_config_rbd}
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@ -378,6 +322,14 @@ please visit [OCF documentation](https://open-cas.github.io/).
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Malloc bdevs are ramdisks. Because of its nature they are volatile. They are created from hugepage memory given to SPDK
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Malloc bdevs are ramdisks. Because of its nature they are volatile. They are created from hugepage memory given to SPDK
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application.
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application.
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Example command for creating malloc bdev:
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`rpc.py bdev_malloc_create -b Malloc0 64 512`
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Example command for removing malloc bdev:
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`rpc.py bdev_malloc_delete Malloc0`
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# Null {#bdev_config_null}
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# Null {#bdev_config_null}
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The SPDK null bdev driver is a dummy block I/O target that discards all writes and returns undefined
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The SPDK null bdev driver is a dummy block I/O target that discards all writes and returns undefined
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@ -460,7 +412,6 @@ User can get list of available lvol stores using `bdev_lvol_get_lvstores` RPC co
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parameters available).
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parameters available).
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Example response
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Example response
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~~~
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~~~
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{
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{
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"uuid": "330a6ab2-f468-11e7-983e-001e67edf35d",
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"uuid": "330a6ab2-f468-11e7-983e-001e67edf35d",
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