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Re: Performance problem - reads slower than writes

To: Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx>
Subject: Re: Performance problem - reads slower than writes
From: Brian Candler <B.Candler@xxxxxxxxx>
Date: Sat, 4 Feb 2012 20:04:17 +0000
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>, xfs@xxxxxxxxxxx
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On Sat, Feb 04, 2012 at 06:49:23AM -0600, Stan Hoeppner wrote:
> Apparently you've read of a different GlusterFS.  The one I know of is
> for aggregating multiple storage hosts into a cloud storage resource.
> It is not designed to replace striping or concatenation of disks within
> a single host.

Sure it can. A gluster volume consists of "bricks". Each brick is served by
a glusterd process listening on a different TCP port. Those bricks can be on
the same server or on different servers.

> Even if what you describe can be done with Gluster, the performance will
> likely be significantly less than a properly setup mdraid or hardware
> raid.  Again, if it can be done, I'd test it head-to-head against RAID.

I'd expect similar throughput but higher latency. Given that I'm using low
RPM drives which already have high latency, I'm hoping the additional
latency will be insignificant.  Anyway, I'll know more once I've done the
measurements.

> I've never been a fan of parity RAID, let alone double parity RAID.

I'm with you on that one.

The attractions of gluster are:
- being able to scale a volume across many nodes, transparently to
  the clients
- being able to take a whole node out of service, while clients
  automatically flip over to the other

Regards,

Brian.

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