# salt.modules.bcache

Module for managing BCache sets

BCache is a block-level caching mechanism similar to ZFS L2ARC/ZIL, dm-cache and fscache. It works by formatting one block device as a cache set, then adding backend devices (which need to be formatted as such) to the set and activating them.

It's available in Linux mainline kernel since 3.10

https://www.kernel.org/doc/Documentation/bcache.txt

This module needs the bcache userspace tools to function.

New in version 2016.3.0.

salt.modules.bcache.attach_(dev=None)

  Attach a backing devices to a cache set If no dev is given, all backing devices will be attached.

  CLI Example:

      salt '*' bcache.attach sdc
      salt '*' bcache.attach /dev/bcache1

  Returns:

    bool or None if nuttin' happened

salt.modules.bcache.back_make(dev, cache_mode='writeback', force=False, attach=True, bucket_size=None)

  Create a backing device for attachment to a set. Because the block size must be the same, a cache set already needs to exist.

  CLI Example:

      salt '*' bcache.back_make sdc cache_mode=writeback attach=True

  Parameters:

    - cache_mode -- writethrough, writeback, writearound or none.

    - force -- Overwrite existing bcaches

    - attach -- Immediately attach the backing device to the set

    - bucket_size -- Size of a bucket (see kernel doc)

salt.modules.bcache.cache_make(dev, reserved=None, force=False, block_size=None, bucket_size=None, attach=True)

  Create BCache cache on a block device. If blkdiscard is available the entire device will be properly cleared in advance.

  CLI Example:

      salt '*' bcache.cache_make sdb reserved=10% block_size=4096

  Parameters:

    - reserved --

      if dev is a full device, create a partition table with this size empty.

      Note

      this increases the amount of reserved space available to SSD garbage collectors, potentially (vastly) increasing performance

    - block_size -- Block size of the cache; defaults to devices' logical block size

    - force -- Overwrite existing BCache sets

    - attach -- Attach all existing backend devices immediately

salt.modules.bcache.config_(dev=None, **kwargs)

  Show or update config of a bcache device.

  If no device is given, operate on the cache set itself.

  CLI Example:

      salt '*' bcache.config
      salt '*' bcache.config bcache1
      salt '*' bcache.config errors=panic journal_delay_ms=150
      salt '*' bcache.config bcache1 cache_mode=writeback writeback_percent=15

  Returns:

    config or True/False

salt.modules.bcache.detach(dev=None)

  Detach a backing device(s) from a cache set If no dev is given, all backing devices will be attached.

  Detaching a backing device will flush its write cache. This should leave the underlying device in a consistent state, but might take a while.

  CLI Example:

      salt '*' bcache.detach sdc
      salt '*' bcache.detach bcache1

salt.modules.bcache.device(dev, stats=False, config=False, internals=False, superblock=False)

  Check the state of a single bcache device

  CLI Example:

      salt '*' bcache.device bcache0
      salt '*' bcache.device /dev/sdc stats=True

  Parameters:

    - stats -- include statistics

    - settings -- include all settings

    - internals -- include all internals

    - superblock -- include superblock info

salt.modules.bcache.start()

  Trigger a start of the full bcache system through udev.

  CLI Example:

      salt '*' bcache.start

salt.modules.bcache.status(stats=False, config=False, internals=False, superblock=False, alldevs=False)

  Show the full status of the BCache system and optionally all its involved devices

  CLI Example:

      salt '*' bcache.status
      salt '*' bcache.status stats=True
      salt '*' bcache.status internals=True alldevs=True

  Parameters:

    - stats -- include statistics

    - config -- include settings

    - internals -- include internals

    - superblock -- include superblock

salt.modules.bcache.stop(dev=None)

  Stop a bcache device If no device is given, all backing devices will be detached from the cache, which will subsequently be stopped.

  Warning

  'Stop' on an individual backing device means hard-stop; no attempt at flushing will be done and the bcache device will seemingly 'disappear' from the device lists

  CLI Example:

      salt '*' bcache.stop

salt.modules.bcache.super_(dev)

  Read out BCache SuperBlock

  CLI Example:

      salt '*' bcache.device bcache0
      salt '*' bcache.device /dev/sdc

salt.modules.bcache.uuid(dev=None)

  Return the bcache UUID of a block device. If no device is given, the Cache UUID is returned.

  CLI Example:

      salt '*' bcache.uuid
      salt '*' bcache.uuid /dev/sda
      salt '*' bcache.uuid bcache0