Re: Replication delay

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On 01/25/2014 03:36 PM, Pranith Kumar Karampuri wrote:


----- Original Message -----
From: "Vijay Bellur" <vbellur@xxxxxxxxxx>
To: "Pranith Kumar Karampuri" <pkarampu@xxxxxxxxxx>
Cc: "Fabio Rosati" <fabio.rosati@xxxxxxxxxxxxxxxxx>, "Gluster-users@xxxxxxxxxxx List" <gluster-users@xxxxxxxxxxx>
Sent: Saturday, January 25, 2014 3:32:24 PM
Subject: Re:  Replication delay

On 01/25/2014 02:28 PM, Pranith Kumar Karampuri wrote:
Vijay,
       But it seems like self-heal's fd is able to perform 'writes'.
       Shouldn't it be uniform if it is the problem with xfs?

The problem is not with xfs alone. It is due to a combination of several
factors including disk sector size, xfs sector size and the nature of
writes being performed. With cache=none, qemu does O_DIRECT open() which
necessitates proper alignment for write operations to happen
successfully. Self-heal does not open() with O_DIRECT and hence write
operations initiated by self-heal go through.

I was also guessing it could be related to O_DIRECT. Anyway to fix that?

One option might be to enable option "network.remote-dio" on the glusterfs volume. Fabio - can you please check if this works?

Wonder why it has to happen only on one of the bricks.

I suspect that the bricks are not completely identical. Hence it does go through on one and fails on the other.

-Vijay


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