Re: expand raid

[Slava Astashonok <sla@0n.ru>]

Nick 'TARANTUL' Novikov wrote:

>>подавать ;) Те, что мне доводилось видеть - нет. Да и сам линукс этому
>>совсем недавно научился.
> 
> А где пишут вот как раз "про это" ?

2.6.17/drivers/md/Kconfig:

config MD_RAID5_RESHAPE
        bool "Support adding drives to a raid-5 array (experimental)"
        depends on MD_RAID5 && EXPERIMENTAL
        ---help---
          A RAID-5 set can be expanded by adding extra drives. This
          requires "restriping" the array which means (almost) every
          block must be written to a different place.

          This option allows such restriping to be done while the array
          is online.  However it is still EXPERIMENTAL code.  It should
          work, but please be sure that you have backups.

          You will need mdadm verion 2.4.1 or later to use this
          feature safely.  During the early stage of reshape there is
          a critical section where live data is being over-written.  A
          crash during this time needs extra care for recovery.  The
          newer mdadm takes a copy of the data in the critical section
          and will restore it, if necessary, after a crash.

          The mdadm usage is e.g.
               mdadm --grow /dev/md1 --raid-disks=6
          to grow '/dev/md1' to having 6 disks.

          Note: The array can only be expanded, not contracted.
          There should be enough spares already present to make the new
          array workable.