[Gluster-users] Replication delay

[Vijay Bellur]

On 01/27/2014 03:40 PM, Fabio Rosati wrote:
> 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 for the confirmation. Yes, network.remote-dio is recommended to 
be on for better performance.

Regards,
Vijay

>
>
> 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
>
>
>