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On 25.11.13 21:24, Eric Browning wrote:
> Steven,
>
> I've tried to 4K align these SSDs with gnop but they are currently ashift
> 9.  Pool layout is just 4 drives in a zfs stripe.  I've also tried raidz1
> with no noticeable performance impacts other than a loss of space for
> parity.
>

ashift=9 with most (all?) SSDs is a big no-no! You really should make 
that pool ashift=12 (at least) and have it 4k aligned (partition).

Especially for writes, an properly aligned 4 drive SSD stripe should be 
way faster.

Here is what I get from ashift=12 raidz1 4 SSD drive pool

# dd if=/dev/zero of=zero bs=1m count=1k
1024+0 records in
1024+0 records out
1073741824 bytes transferred in 1.817027 secs (590933382 bytes/sec)

Unfortunately, your only option is dump / recreate pool / restore. (zfs 
send/receive is an option too -- especially if you have another set of 
drives)


Daniel