On Wed, Oct 5, 2016 at 2:14 PM, Gandalf Corvotempesta <gandalf.corvotempesta@xxxxxxxxx> wrote:
2016-10-05 20:50 GMT+02:00 David Gossage <dgossage@xxxxxxxxxxxxxxxxxx>:
> 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?
L2ARC filled up some, but the usage hit ratios never hit above 8% so I just freed it up fro the system to use as it would. Haven;t noticed any difference since doing that.
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 ?
L2ARC is per pool I believe.
> 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
That's fine. For my VM case I currently only use around 1TB per host so worst case scenario I found was if one server is down I could rebuild brick overnight. For your case that's not as easy. Also for me I use 1TB disks in my mirrors so if one drive goes down it's not that long to re-sync it on replace. Reduces my chance to have 2 disks in same mirror die at same time a little bit.
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,
right?
Is possible to change the ZIL flush timeout from 5 seconds to
something bigger as i'm using SSD with power-loss protection ?
I believe you can though I haven't played with that.
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