[OmniOS-discuss] Slow scrub on SSD-only pool

[Stephan Budach]

Hi all,

I am running a scrub on a SSD-only zpool on r018. This zpool consists of 
16 iSCSI targets, which are served from two other OmniOS boxes - 
currently still running r016 over 10GbE connections.

This zpool serves as a NFS share for my Oracle VM cluster and it 
delivers reasonable performance. Even while the scrub is running, I can 
get approx 1200MB/s throughput when dd'ing a vdisk from the ZFS to 
/dev/null.

However, the running scrub is only progressing like this:

root at zfsha02gh79:/root# zpool status ssdTank
   pool: ssdTank
  state: ONLINE
   scan: scrub in progress since Sat Apr 16 23:37:52 2016
     68,5G scanned out of 1,36T at 1,36M/s, 276h17m to go
     0 repaired, 4,92% done
config:

         NAME STATE     READ WRITE CKSUM
         ssdTank ONLINE       0     0     0
           mirror-0 ONLINE       0     0     0
             c3t600144F090D09613000056B8A76C0001d0 ONLINE       0     
0     0
             c3t600144F090D09613000056B8A93C0009d0 ONLINE       0     
0     0
           mirror-1 ONLINE       0     0     0
             c3t600144F090D09613000056B8A7BE0002d0 ONLINE       0     
0     0
             c3t600144F090D09613000056B8A948000Ad0 ONLINE       0     
0     0
           mirror-2 ONLINE       0     0     0
             c3t600144F090D09613000056B8A7F10003d0 ONLINE       0     
0     0
             c3t600144F090D09613000056B8A958000Bd0 ONLINE       0     
0     0
           mirror-3 ONLINE       0     0     0
             c3t600144F090D09613000056B8A7FC0004d0 ONLINE       0     
0     0
             c3t600144F090D09613000056B8A964000Cd0 ONLINE       0     
0     0
           mirror-4 ONLINE       0     0     0
             c3t600144F090D09613000056B8A8210005d0 ONLINE       0     
0     0
             c3t600144F090D09613000056B8A96E000Dd0 ONLINE       0     
0     0
           mirror-5 ONLINE       0     0     0
             c3t600144F090D09613000056B8A82E0006d0 ONLINE       0     
0     0
             c3t600144F090D09613000056B8A978000Ed0 ONLINE       0     
0     0
           mirror-6 ONLINE       0     0     0
             c3t600144F090D09613000056B8A83B0007d0 ONLINE       0     
0     0
             c3t600144F090D09613000056B8A983000Fd0 ONLINE       0     
0     0
           mirror-7 ONLINE       0     0     0
             c3t600144F090D09613000056B8A84A0008d0 ONLINE       0     
0     0
             c3t600144F090D09613000056B8A98E0010d0 ONLINE       0     
0     0

errors: No known data errors

These are all Intel S3710s with 800GB and I can't seem to find out why 
it's moving so slowly.
Anything I can look at specifically?

Thanks,
Stephan