[mythtv-users] Poor performance with ZFS (ZFS on Linux)

[Rajil Saraswat]

On 05/30/2018 08:06 AM, Dan Wilga wrote:
> In addition to the well thought-out advice of Stephen, I'll mention
> that there are two features of ZFS which can also reduce its
> performance significantly: compression and deduplication. If you have
> either of these enabled, you can easily try disabling them temporarily.
>
> # zfs get compression,dedup my_zfs
> NAME  PROPERTY     VALUE          SOURCE
> my_zfs  compression  lz4            local
> my_zfs  dedup        on             local
>
> # zfs set compression=off my_zfs
> # zfs set dedup=off my_zfs
>
> Repeat your tests and re-enable whichever features need to be re-enabled.

I dont have dedup enabled but compression was on. I turned it off and
restarted mariadb server. Unfortunately, it did not affect the time to
run mythfilldatabase.

# zfs get compression rpool/db rpool/db/innodb rpool/db/logs
NAME             PROPERTY     VALUE     SOURCE
rpool/db         compression  off       local
rpool/db/innodb  compression  off       inherited from rpool/db
rpool/db/logs    compression  off       inherited from rpool/db

The ZFS is hosted on a mirror  of Intel S3500 SSD (300 GB) which is 60%
occupied,

# zfs list rpool rpool/db rpool/db/innodb rpool/db/logs
NAME              USED  AVAIL  REFER  MOUNTPOINT
rpool             103G   166G    96K  none
rpool/db          194M   166G   157M  /var/lib/mysql
rpool/db/innodb  2.09M   166G  2.09M  /var/lib/mysql/innodb
rpool/db/logs    34.9M   166G  34.9M  /var/lib/mysql/logs


When running mythfilldatabase the arc usage is as follows,

# arcstat.py 10 10
    time  read  miss  miss%  dmis  dm%  pmis  pm%  mmis  mm%  arcsz     c 
07:16:19     1     0     50     0   50     0    0     0    0   3.7G  5.8G 
07:16:29  3.2K  1.5K     46  1.5K   46     0    0     0    0   3.7G  5.8G 
07:16:39  3.3K  1.5K     46  1.5K   46     0    0     0    0   3.7G  5.8G 
07:16:49  3.3K  1.4K     43  1.4K   43     0    0     4    0   3.8G  5.8G 
07:16:59  3.2K  1.5K     46  1.5K   46     0    0     0    0   3.8G  5.8G 
07:17:09  1.9K   732     39   732   39     0    0     2    0   3.8G  5.8G 
07:17:19  1.8K   757     42   757   43     0    0     0    0   3.8G  5.8G 
07:17:29  1.7K   739     43   739   43     0    0     0    0   3.8G  5.8G 
07:17:39  1.7K   703     42   703   42     0    0     0    0   3.8G  5.8G 
07:17:49  1.8K   724     40   724   40     0    0     0    0   3.8G  5.8G


# free -h
              total        used        free      shared  buff/cache  
available
Mem:           11Gi       6.8Gi       4.2Gi       119Mi      
743Mi       4.6Gi
Swap:         4.0Gi          0B       4.0Gi