[mythtv-users] Some master/slave backend advise required

[Johan van der Kolk]

On Tue, Jun 3, 2014 at 7:44 AM, Jean-Yves Avenard <jyavenard at gmail.com>
wrote:

> On 3 June 2014 15:35, Johan Van der Kolk <johan.vanderkolk at gmail.com>
> wrote:
>
> > For those who understand bonnie ( i don’t). This is a command line taken
> > from https://calomel.org/zfs_raid_speed_capacity.html.
> > I ran it on my zfspool.
> >
> > Version  1.97       ------Sequential Output------ --Sequential Input-
> > --Random-
> > Concurrency   1     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block--
> > --Seeks--
> > Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP
>  /sec
> > %CP
> > Zolder-server   80G           318688  37 136544  25           269337  20
> > 38.6   2
> > Latency                        4301ms    1176ms               549ms
> > 658ms
> >
>
> beware with Bonnie, more often than not (and that's certainly the case
> with the calomel review), due to the arguments provided what they are
> really testing is the cache and memory speed, and rarely the actual
> raw I/O to the disk.
>
> 136MB/s on 6 disks in RAIDZ2 is rather low, much lower than I would
> have expected (mine gives me over 400MB/s of raw I/O under similar
> conditions)
>

It's an "out of the box installation" from the zfs repository. Ran out of
time to understand and tune the parameters. But it worked, met the
requirements at the time.
Probably not a bad idea to see what can be tweaked. There is still a
possibility to move all data to the SSD or another disk and meanwhile
optimize the ZFS.
But it looks like ZFS is not my main bottleneck. Even at a poor 139MB/s it
manages to write 500GB per hour. (theoretically, and with reservations with
regards to the measurement method)


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