Improvements on ZFS’ scrub speed in r339034

r339034 introduced some improvement in stable/11 when ZFS performs scans, e.g. scrubbing.

Here’s the stats before running a new scrub:

  pool: zroot
 state: ONLINE
  scan: scrub repaired 0 in 0 days 00:05:35 with 0 errors on Tue Oct  2 03:06:55 2018
config:

        NAME            STATE     READ WRITE CKSUM
        zroot           ONLINE       0     0     0
          raidz1-0      ONLINE       0     0     0
            gpt/zroot0  ONLINE       0     0     0
            gpt/zroot1  ONLINE       0     0     0
            gpt/zroot2  ONLINE       0     0     0

errors: No known data errors

Here’s the stats shortly after issuing the new scrub:

  pool: zroot
 state: ONLINE
  scan: scrub in progress since Wed Oct  3 12:32:04 2018
        1.72G scanned at 883M/s, 0 issued at 0/s, 23.0G total
        0 repaired, 0.00% done, no estimated completion time
config:

        NAME            STATE     READ WRITE CKSUM
        zroot           ONLINE       0     0     0
          raidz1-0      ONLINE       0     0     0
            gpt/zroot0  ONLINE       0     0     0
            gpt/zroot1  ONLINE       0     0     0
            gpt/zroot2  ONLINE       0     0     0

errors: No known data errors

Here’s the stats shortly before finishing:

  pool: zroot
 state: ONLINE
  scan: scrub in progress since Wed Oct  3 12:32:04 2018
        23.0G scanned at 277M/s, 22.7G issued at 274M/s, 23.0G total
        0 repaired, 98.82% done, 0 days 00:00:01 to go
config:

        NAME            STATE     READ WRITE CKSUM
        zroot           ONLINE       0     0     0
          raidz1-0      ONLINE       0     0     0
            gpt/zroot0  ONLINE       0     0     0
            gpt/zroot1  ONLINE       0     0     0
            gpt/zroot2  ONLINE       0     0     0

errors: No known data errors

Here’s the final stats:

  pool: zroot
 state: ONLINE
  scan: scrub repaired 0 in 0 days 00:01:26 with 0 errors on Wed Oct  3 12:33:30 2018
config:

        NAME            STATE     READ WRITE CKSUM
        zroot           ONLINE       0     0     0
          raidz1-0      ONLINE       0     0     0
            gpt/zroot0  ONLINE       0     0     0
            gpt/zroot1  ONLINE       0     0     0
            gpt/zroot2  ONLINE       0     0     0

errors: No known data errors

5 minutes and 35 seconds ± 1 second vs. 1 minute and 26 seconds ± 1 second. That’s an improvement of 4 minutes and 9 seconds ± 2 seconds. The ratio being 335/86 ≈ 3.89534883721. The amount of data stored didn’t change much between these two runs.

Published by

Trond Endrestøl

I stopped counting my age years ago. Personal interests besides computers and computer networks include, but not limited to, astronomy, comics, music, and science (fiction).

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