Provided by: flashcache-utils_3.1.3+git20150701-2ubuntu2_i386 bug


       flashcache_create - create a new flashcache volume


       flashcache_create  initializes  a new flashcache volume from unformated
       block devices.  It  creates  flashcache  meta  data  and  provides  new
       volumes though their volume mappings.


       flashcache_create  -p  back|around|thru [-s cache size] [-b block size]
       [-v] cachedevname cache_devname disk_devname


       -v     verbose

       -p     cache mode.  Required argument.  Specify any  supported  option:
              (write-)back,  (write-)thru or (write-)around.  Their respective
              implications are denoted below.

       -s     cache size.  Optional argument.  By default, flashcache will use
              the  auto-detected  full  cache  device size.  When present, the
              given cache size  is  used  instead.   The  expected  units  are
              sectors, however any value can be suffixed by "k", "m" or "g" to
              interpret  the   argument   in   kilo-,   mega-   or   gigabytes

       -b     block  size.   Optional  argument.   Defaults to 4KB.  Must be a
              power of 2.  The default units is sectors.  However,  k  can  be
              specified as unit type as well.  (A 4KB blocksize is the correct
              choice for the vast majority of applications.

       -f     force create.  Bypass all sanity checks  (for  example  for  the
              sector size).  Use with care.


       The following caching modes are supported:

       Writethrough  (thru)  - safest mode, all writes are cached to the cache
       device but are also being written to disk  immediately.   If  the  used
       cache  device has a lower write performance than the backend disk (many
       early generation SSD drives manufactured between  2008-2010  are  known
       for  such  a poor write performance) enabling the writethrough mode may
       decrease the system write  performance.   All  disk  reads  are  cached
       (tunable through flashcache's /proc interface).

       Writearound (ardound) - again, very safe, writes are not written to the
       cache device, but directly to the backend disk  instead.   Disk  blocks
       will  only  be  cached  after they are read.  All disk reads are cached
       (tunable through flashcache's /proc interface).

       Writeback (back) - fastest mode but less safe.  Writes only go  to  the
       cache  device  initially,  and  are  being  written to the backend disk
       later, depending on configured system  policie.   All  disk  reads  are
       cached (tunable through flashcache's /proc interface).


       Writethru  and  Writearound  caches  are not persistent across a device
       removal or a reboot.   Only  Writeback  caches  are  persistent  across
       device  removals  and reboots.  This reinforces 'writeback is fastest',
       'writethrough is safest'.


       flashcache_create -p back -s 1g -b 4k cachedev /dev/sdc /dev/sdb
              Creates a 1GB writeback cache volume with a 4KB  block  size  on
              the  cache  device  /dev/sdc  to cache the disk volume /dev/sdb.
              The name of the device created is "cachedev".

       flashcache_create -p thru -s 2097152 -b 8 cachedev /dev/sdc /dev/sdb
              Same as above but creates  a  write  through  cache  with  units
              specified in sectors instead.  The name of the device created is


       flashcache_load(8), flashcache_destroy(8)

       README and  other  documents  in  /usr/share/doc/flashcache-utils.   In
       particular,  see flashcache-sa-guide.txt for configuring the flashcache
       kernel module through its /proc interface.

       The flashcache source code and all documentation may be downloaded from


       Flashcache is developed by Mohan Srinivasan <>

       This  man  page  was written by Dmitry Smirnov <>
       for Debian GNU/Linux (but may be used by others).