[zfs-discuss] use of raid card question

Gregor Kopka gregor at kopka.net
Thu Apr 12 07:17:32 EDT 2012


Am 12.04.2012 04:08, schrieb Salvatore Giudice:
> BTW, raid 10 is easy to setup in ZFS. Please beaware that it is not called 'raid 10' in reference to ZFS. In ZFS it's referred to as a 'stripe of mirrors'. To construct such a setup, you would need to_create all your mirrored pairs as vdevs first_._Then_  assemble those into a striped zpool.
This is misleading. The moment you create a vdev it'll belong to a pool 
(thus can't be assembled in another).

Options to create raid10 style pools in ZFS:

_directly create pool with mirrored vdevs (mirrored stripes):_
$ zpool create /pool/ mirror /dev1 dev2/ mirror /dev3 dev4
//
/_create striped pool fist, then mirror them:_
$ zpool create /pool dev1 dev3 /    # pool with 2 vdevs
$ zpool attach /pool dev1 dev2/        # mirror 1st vdev
$ zpool attach /pool dev3 dev4/        # mirror 2nd vdev
/
/_add more stripes and mirrors later:_
$ zpool add /pool //dev5                # add another vdev (stripe)/
$ zpool attach /pool dev5 dev6/        # mirror it/
  - or -
$ zpool /add /pool /mirror /dev5 dev6/    # add mirrored as vdev/
///__/
/Just remember that you're able to detach devices from a mirrored vdev 
/as long as one device is left in the vdev/, *but you can't remove a 
vdev from a pool*!

Do yourself the favour of letting ZFS handle the mirroring/striping, 
don't let a controller card do it (or you'll disable features which make 
ZFS great, like resilvering)

Gregor
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