[Gluster-users] Gluster-users Digest, Vol 76, Issue 18 - Re: reading not distributed across bricks

Ben England bengland at redhat.com
Tue Aug 12 12:48:50 UTC 2014

> Message: 1
> Date: Mon, 11 Aug 2014 09:53:30 -0400 (EDT)
> From: Justin Clift <justin at gluster.org>
> To: Pranith Kumar Karampuri <pkarampu at redhat.com>
> Cc: gluster-users at gluster.org, Ray Mannings <manningsray1 at gmail.com>
> Subject: Re: [Gluster-users] Reading not distributed across bricks
> Message-ID:
> 	<417182971.4749068.1407765210056.JavaMail.zimbra at redhat.com>
> Content-Type: text/plain; charset=utf-8
> ----- Original Message -----
> > hi Ray,
> >    Reads are served from the bricks which respond the fastest at the
> > moment. They are not load-balanced.
> Maybe a good feature for 3.7? :)

There already is a feature, from gluster volume set help:
"Option: cluster.read-hash-mode
Description: inode-read fops happen only on one of the bricks in replicate. AFR will prefer the one computed using the method specified using this option
0 = first responder, 
1 = hash by GFID of file (all clients use same subvolume), 
2 = hash by GFID of file and client PID"

This is particularly useful for benchmark tests, where the system may not have response time data sufficient to properly load balance and I have seen all the clients select the same replica using default value of 0.  The value 2 is nice because if many clients are reading the same file, the load is distributed across bricks.

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