Mirror of Raidz for data reliability

[Paul Schenkeveld]

On Mon, May 14, 2012 at 01:35:51AM +0800, Marcelo Araujo wrote:
> Hi All,
> 
> Me and a co-work are working in a new feature for ZFS, we have 2 Machines
> and 2 JBOD, every Machine are connected on those JBOD via SAS and we are
> trying to make a fail-over server. Currently every each Machine has two SAS
> cables, each one connected in both JBOD.
> 
> We have worked last week to figure out, how we could make the data be
> always alive in case one JBOD dies, and let me show you my console output
> ;):
> 
> controllerA# zpool status -v araujo
>   pool: araujo
>  state: ONLINE
>  scan: resilvered 57K in 0h0m with 0 errors on Sat May 12 14:32:29 2012
> config:
> 
>         NAME          STATE     READ WRITE CKSUM
>         araujo        ONLINE       0     0     0
>           raidz1-0    ONLINE       0     0     0
>             mirror-0  ONLINE       0     0     0
>               da0     ONLINE       0     0     0
>               da3     ONLINE       0     0     0
>             mirror-1  ONLINE       0     0     0
>               da1     ONLINE       0     0     0
>               da4     ONLINE       0     0     0
>             mirror-2  ONLINE       0     0     0
>               da2     ONLINE       0     0     0
>               da5     ONLINE       0     0     0
> 

Maybe a dumb question, how you you create the above setup?  I seem unable
to create a raidz consisting of mirrors neither can I attach a second
physical drive to an existing one in a raidz of three single drives:

  # zpool create tank raidz1 mirror /dev/da0 /dev/da3 mirror /dev/da1 /dev/da4 mirror /dev/da2 /dev/da5
  invalid vdev specification: raidz1 requires at least 2 devices

  # zpool create tank raidz1 /dev/da0 /dev/da1 /dev/da2
  # zpool attach tank /dev/da0 /dev/da3
  cannot attach /dev/da3 to /dev/da0: can only attach to mirrors and top-level disks

  # zpool upgrade
  This system is currently running ZFS pool version 28.

  All pools are formatted using this version.

Kind regards,

Paul Schenkeveld