[Gluster-users] Replication delay

[Fabio Rosati]

Vijay,

   I can confirm that enabling network.remote-dio on the volume solves the problem.
Do you think this is the best option also for performace?


Thanks a lot
Fabio

----- Messaggio originale -----
Da: "Vijay Bellur" <vbellur at redhat.com>
A: "Pranith Kumar Karampuri" <pkarampu at redhat.com>
Cc: "Fabio Rosati" <fabio.rosati at geminformatica.it>, "Gluster-users at gluster.org List" <gluster-users at gluster.org>
Inviato: Sabato, 25 gennaio 2014 11:25:01
Oggetto: Re: [Gluster-users] Replication delay

On 01/25/2014 03:36 PM, Pranith Kumar Karampuri wrote:
>
>
> ----- Original Message -----
>> From: "Vijay Bellur" <vbellur at redhat.com>
>> To: "Pranith Kumar Karampuri" <pkarampu at redhat.com>
>> Cc: "Fabio Rosati" <fabio.rosati at geminformatica.it>, "Gluster-users at gluster.org List" <gluster-users at gluster.org>
>> Sent: Saturday, January 25, 2014 3:32:24 PM
>> Subject: Re: [Gluster-users] 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