Gluster users - Nov 2015 - File Corruption with shards - 100% reproducable

Lindsay, 

I wanted to ask you one more thing: specifically in VM workload with sharding,
do you run into consistency issues with strict-write-ordering being off?
I remember suggesting that this option be enabled. But that was for plain dd on
the mountpoint (and not inside the vm), where it was necessary.
I want to know if it is *really* necessary in VM workloads. 

-Krutika 

----- Original Message -----
> From: "Lindsay Mathieson" <lindsay.mathieson at gmail.com>
> To: "Krutika Dhananjay" <kdhananj at redhat.com>
> Cc: "gluster-users" <gluster-users at gluster.org>
> Sent: Sunday, November 15, 2015 11:39:57 AM
> Subject: Re: [Gluster-users] File Corruption with shards - 100%
reproducable
> On 15 November 2015 at 13:32, Krutika Dhananjay < kdhananj at redhat.com
>
> wrote:
> > So to start with, just disable performance.stat-prefetch and leave the
rest
> > of the options as they were before and run the test case.
> 
> Yes, that seems to be the guilty party. When disabled I can freely migrate
> VM's, emabled, things rapidly go pear shaped.
> --
> Lindsay
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On 19/11/15 14:49, Krutika Dhananjay wrote:
> I wanted to ask you one more thing: specifically in VM workload with 
> sharding, do you run into consistency issues with 
> strict-write-ordering being off?
> I remember suggesting that this option be enabled. But that was for 
> plain dd on the mountpoint (and not inside the vm), where it was 
> necessary.
> I want to know if it is *really* necessary in VM workloads.

Hi Krutika, sorry for the delay, have been head down with work and sick 
doggies :(

No I didn't need strict-write-ordering off/on, the VM's were fine. It 
was only stat-prefetch that needed to be off.

One caveat - I started testing with 3.7.5, then upgraded to 3.7.6, but 
didn't upgrade the op-version (always forget that).

Once I set the op version to 3.7.6 sharded volumes started reporting 
correct file sizes (for new files) even with strict-write-ordering off. 
However disk usage was still out by a lot.