[Gluster-users] Production cluster planning

Gandalf Corvotempesta gandalf.corvotempesta at gmail.com
Wed Oct 5 19:14:07 UTC 2016

2016-10-05 20:50 GMT+02:00 David Gossage <dgossage at carouselchecks.com>:
> The mirrored slog will be useful.  Depending on what you put on the pool
> l2arc may not get used much.  I removed mine as it got such a low hit rate
> serving VM's.

I'll use shards. The most accessed shard isn't cached in L2ARC?

I'll also other pools for plain file hosting (websites and so one). In
this case an L2ARC would be usefull. I think.
Is possible to share the same L2ARC from multiple ZFS pools ?

> I also re-did my bricks from raidz2 to using mirrored pairs. I felt that
> with 3 server redundancy the performance benefits from a more raid10 type
> layout would be more useful than raidz2 for the pool.  I could see where
> some might want more security though in their data

So, you removed the RAIDZ2 and created multiple mirrors (like RAID-1) ?
I can do that, but is really a waste of space. In a replica 3, your
are replicating 6 times.
Or did you create a RAID-10 ? I really hate RAID-10. If you loose 2
disks from the same mirror
(and in a 12 disks server this could be frequent) you loose the whole
pool and rebuilding time from
the network could be.............. HUGE. Try to rebuild 24TB from
network. In a perfect world, this require
at least 24.000/1.24 = 19.200 seconds. more than 5 hours by using the
whole 10GB network only for healing.

I feel more confortable with 2xRAIDZ-2 than a RAID10

By using SLOG, the RAIDZ2 write penalty should be removed as gluster
always write to SLOG (SSD) and to the RAIDZ-2 only in background,
Is possible to change the ZIL flush timeout from 5 seconds to
something bigger as i'm using SSD with power-loss protection ?

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