How to speed up slow zpool scrub?

[Jeremy Faulkner]

zfs get all tank0

On 2016-04-26 9:35 AM, Miroslav Lachman wrote:
> InterNetX - Juergen Gotteswinter wrote on 04/26/2016 15:09:
>> to speed up the scrub itself you can try
>>
>> sysctl -w vfs.zfs.scrub_delay = 4 (default, 0 means higher prio)
>
> I will try it in the idle times
>
>> but be careful as this can cause a serious performance impact, the value
>> can be changed on the fly
>>
>> your pool is raidz, mirror ? dedup is hopefully disabled?
>
> I forgot to mention it. Disks are partitioned to four partitions:
>
> # gpart show -l ada0
> =>        34  7814037101  ada0  GPT  (3.6T)
>            34           6        - free -  (3.0K)
>            40        1024     1  boot0  (512K)
>          1064    10485760     2  swap0  (5.0G)
>      10486824    31457280     3  disk0sys  (15G)
>      41944104  7769948160     4  disk0tank0  (3.6T)
>    7811892264     2144871        - free -  (1.0G)
>
> diskXsys partitions are used for base system pool which is 4-way mirror
>
> diskXtank0 partitions are used for data storage as RAIDZ
>
> # zpool list
> NAME    SIZE  ALLOC   FREE  EXPANDSZ   FRAG    CAP  DEDUP  HEALTH  ALTROOT
> sys    14.9G  11.0G  3.92G         -    79%    73%  1.00x  ONLINE  -
> tank0  14.4T  10.8T  3.56T         -    19%    75%  1.00x  ONLINE  -
>
>
> # zpool status -v
>    pool: sys
>   state: ONLINE
>    scan: scrub repaired 0 in 1h2m with 0 errors on Sun Apr 24 04:03:54 2016
> config:
>
>          NAME              STATE     READ WRITE CKSUM
>          sys               ONLINE       0     0     0
>            mirror-0        ONLINE       0     0     0
>              gpt/disk0sys  ONLINE       0     0     0
>              gpt/disk1sys  ONLINE       0     0     0
>              gpt/disk2sys  ONLINE       0     0     0
>              gpt/disk3sys  ONLINE       0     0     0
>
> errors: No known data errors
>
>    pool: tank0
>   state: ONLINE
>    scan: scrub in progress since Sun Apr 24 03:01:35 2016
>          7.63T scanned out of 10.6T at 36.7M/s, 23h32m to go
>          0 repaired, 71.98% done
> config:
>
>          NAME                STATE     READ WRITE CKSUM
>          tank0               ONLINE       0     0     0
>            raidz1-0          ONLINE       0     0     0
>              gpt/disk0tank0  ONLINE       0     0     0
>              gpt/disk1tank0  ONLINE       0     0     0
>              gpt/disk2tank0  ONLINE       0     0     0
>              gpt/disk3tank0  ONLINE       0     0     0
>
> errors: No known data errors
>
>
> # zdb | grep ashift
>              ashift: 12
>              ashift: 12
>
>
> Thank you for your informations.
>
>