flashcache-utils for Debian
---------------------------

 *  flashcache-utils installs a udev handler to invoke
    `/sbin/flashcache_load` for every available block device. This allows one to
    mount Flashcache devices from `/etc/fstab`. To mount a flashcache enabled
    device from `/etc/fstab` first a mapping between a cached device and a cache
    should be established. It can be done using command adapted to personal
    requirements like:

        flashcache_create -p back cache_dev /dev/SSD /dev/disk/by-id/SLOW_DISK

    This makes `/dev/mapper/cache_dev` a pass-through block device which can
    be mounted directly, or from `/etc/fstab` after creating a filesystem on
    it by using the following entry:

        /dev/mapper/cache_dev   /mnt/slow_d   ext4   defaults   0   0

    After a reboot the mapping between `/dev/disk/by-id/SLOW_D` and `/dev/SSD`
    can be restored by invoking the command below which recreates
    `/dev/mapper/cache_dev`:

        /sbin/flashcache_load /dev/ssd

    This is exactly what the udev handler does as well. Please note that
    scanning for available partitions as performed by utilities like gparted,
    will wake up udev and mount existing Flashcache device(s) unless already
    mounted.

 *  Because block devices may be arbitrarly (re-)named, it should be avoided to
    use device names like `/dev/sd[a-z]`. It is recommended to create the
    Flashcache device using `/dev/disk/by-id/<id>` identifiers or by using
    `/dev/disk/by-uuid/<uuid>` instead. For the latter case, the file system
    should exist prior to `/sbin/flashcache_create` invocation. The blkid(8)
    utility may be useful to find UUID of a file system to cache.

 *  Using Flashcache for root file system is not supported.

 *  WARNING: Although it is possible to mount a cached file system after
    binding it to flashcache device, this is going to cause irrevocable data
    corruption if that is tried without destroying the Flashcache device by
    using `/sbin/flashcache_destroy` first. If a write-back Flashcache device
    associated with a disk or partition, all access to such a disk or partition
    should be done through the Flashcache device mapping only.

 *  WARNING: Data corruption has been reported when using a loopback device
    for the cache device.

 *  Please read Flashcache documentation in
    `/usr/share/doc/flashcache-utils`
    and familiarise yourself with basic concepts and commands.
