[Gluster-users] Production cluster planning

Gandalf Corvotempesta gandalf.corvotempesta at gmail.com
Tue Sep 27 21:15:20 UTC 2016

2016-09-26 23:08 GMT+02:00 Lindsay Mathieson <lindsay.mathieson at gmail.com>:
> I wouldn't be doing that - very high risk of gluster corruption in the event
> of power loss or server crash. Up to 5 seconds of writes could be lost that
> way.
> If writes aren't fast enough I'd add a SSD partition for slog. Preferably a
> data center quality one.

You are right, I don't want to loose some data by using 'sync=disabled'
Also, I would like to try to force the use of SLOG to an Enterprise
SSD (also used for L2ARC) by setting 'sync=always'
In this way all writes are synchronous and made against the SSD. This
should also "hide" the overhead of RAIZ2 or RAIDZ3 as writes are on
SLOG and not directly on the vpool

2x Enterprise SSD (Intel 3600)
1 partition on both is mirrored and used as SLOG
The other 2 partitions (one on each SSD) are used as L2ARC and not
mirrored (is not possible and has nonsense)
Everything configure with 'sync=always'
RAIDZ-3 made with 12x 4TB disks (I don't know the resilvering time for
a huge vpool like this)

In this way, an SSD failure doesn't cause data loss (SLOG is mirrored)
and L2ARC cache is automatically disabled by ZFS
At the same time, there isn't any write penalty for the RAIZ3 because
all writes are made to the SLOG and only after that wrote on the pool

What do you think?

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