Ahoy. I just thought I'd add a data point to the mix. I have an 11-disk v13 pool comprised of 400-GB disks on an 8.1 amd64 system and the machine behaves just fine with it:

# zpool status
  pool: archive
 state: ONLINE
status: The pool is formatted using an older on-disk format.  The pool can
        still be used, but some features are unavailable.
action: Upgrade the pool using 'zpool upgrade'.  Once this is done, the
        pool will no longer be accessible on older software versions.
scrub: resilver completed after 0h0m with 0 errors on Fri Oct 8 17:56:52 2010
config:

        NAME        STATE     READ WRITE CKSUM
        archive     ONLINE       0     0     0
          raidz1    ONLINE       0     0     0
            ad4     ONLINE       0     0     0  133K resilvered
            ad6     ONLINE       0     0     0  84K resilvered
            ad8     ONLINE       0     0     0  85.5K resilvered
            ad10    ONLINE       0     0     0  84.5K resilvered
            ad12    ONLINE       0     0     0  88K resilvered
            ad14    ONLINE       0     0     0  83.5K resilvered
            ad16    ONLINE       0     0     0  83K resilvered
            ad18    ONLINE       0     0     0  84.5K resilvered
            ad20    ONLINE       0     0     0  85.5K resilvered
            ad22    ONLINE       0     0     0  84K resilvered
            ad24    ONLINE       0     0     0  86.5K resilvered

errors: No known data errors

-Boris

On 10/20/10 13:26, Sean Thomas Caron wrote:
Hi Lawrence,

Interesting; have you tried this for raidz2 as well?

I just created a raidz2 pool with 5 disks and then added another 5 disk raidz2 to it, so, total of 10 disks in the pool (though this is ultimately a losing strategy unless the number of disks is >> 9 because two drives are lost for parity in each sub-raid in the pool).

It (seemed) just slightly more stable than creating a single raidz2 pool with > 9 disks but it still crashes.

I guess this does allow me to say its more an issue of number of devices in the pool versus capacity of the pool because with the parity drives taken out, the pool with two 5-disk raidz2s has less total capacity than a pool with a single 9-disk raidz2.

Just out of idle curiousity, I also tried it with raidz1 on my system. Again, I created a 5-disk pool, raidz1 this time, then added another 5-disk raidz1 to the pool for, again, total of 10 disks.

Again, a bit of a losing strategy versus creating one great big raidz unless the number of disks is >> 9 because of losing a disk in each sub-raidz1 in the pool for parity but less so of course than raidz2.

This seemed to crash too, same behavior.

Are you using 8.1-RELEASE or STABLE or ...?

Best,

-Sean


I have a 16 disk pool, if you create it with

zpool create poolname raidz disk1 disk2 disk3 etc

then

zpool add poolname raidz disk8 disk9 disk10 etc

You get the full size pool and no issues.

  pool: tank
 state: ONLINE
scan: scrub repaired 0 in 0h0m with 0 errors on Wed Oct 20 14:54:08 2010
config:

        NAME        STATE     READ WRITE CKSUM
        tank        ONLINE       0     0     0
          raidz1-0  ONLINE       0     0     0
            da0     ONLINE       0     0     0
            da1     ONLINE       0     0     0
            da2     ONLINE       0     0     0
            da3     ONLINE       0     0     0
            da4     ONLINE       0     0     0
            da5     ONLINE       0     0     0
            da6     ONLINE       0     0     0
            da7     ONLINE       0     0     0
          raidz1-1  ONLINE       0     0     0
            da8     ONLINE       0     0     0
            da9     ONLINE       0     0     0
            da10    ONLINE       0     0     0
            da11    ONLINE       0     0     0
            da12    ONLINE       0     0     0
            da13    ONLINE       0     0     0
            da14    ONLINE       0     0     0
            da15    ONLINE       0     0     0

errors: No known data errors


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