zpool scrub speed

devsk devsku at gmail.com
Sat May 7 11:28:02 EDT 2011


Just throwing in my numbers for RAIDZ2 in there. This is a zfs-fuse
pool which I upgraded to version 26 today. The numbers seem better
with version 26 compared to 23 (I had compared numbers for version 23
for zfs-fuse and native zfs recently).

# zpool status -v
  pool: mydata
 state: ONLINE
   see: http://www.sun.com/msg/ZFS-8000-EY
 scan: scrub in progress since Sat May  7 08:07:12 2011
    182G scanned out of 1.42T at 365M/s, 0h59m to go
    0 repaired, 12.44% done

This will slow down I guess as time passes. It has typically taken
about 3 hrs in the past.

-devsk


On May 6, 8:29 am, "Jason J. W. Williams" <jasonjwwilli... at gmail.com>
wrote:
> Depends on how fragmented the volume is and how much data is in the pool (it'll only scrub the amount of data in the pool as opposed to scrubbing freespace). Had to scrub an onv_131 system the other night...22x 7200rpm disks with 247gb of data took about 19mins.
>
> I've seen a 14 drive (7200rpm) pool with 1.8tb of data (raid-z2) take over a day to scrub due to failing disks. If you start to see lots of checksum errors on the drives you'll see a long scrub.
>
> -J
>
> Sent via iPhone
>
> Is your e-mail Premiere?
>
> On May 6, 2011, at 2:07, Gordan Bobic <gordan.bo... at gmail.com> wrote:
>
>
>
>
>
>
>
> > What is the general performance expected from zfs scrub? I would have expected it to be in the region of the combined read speed of the data bearing disks (i.e. excluding the parity disks). But my 13 disk array only gets about 170MB/s on a scrub. Is this normal, i.e. explained by the disk-seeking required?
>
> > Gordan



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