----- 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? Wonder why it has to happen only on one of the bricks. Pranith > > -Vijay > > > > > Pranith > > ----- Original Message ----- > >> From: "Vijay Bellur" <vbellur@xxxxxxxxxx> > >> To: "Fabio Rosati" <fabio.rosati@xxxxxxxxxxxxxxxxx>, "Pranith Kumar > >> Karampuri" <pkarampu@xxxxxxxxxx> > >> Cc: "Gluster-users@xxxxxxxxxxx List" <gluster-users@xxxxxxxxxxx> > >> Sent: Saturday, January 25, 2014 1:23:52 PM > >> Subject: Re: Replication delay > >> > >> On 01/24/2014 09:24 PM, Fabio Rosati wrote: > >> > >>> > >>> > >>> The block size is the same, 4096 bytes. > >>> I did some other investigation and it seems the problem happens only with > >>> VM disk images internally formatted with a blocksize of 1024 bytes. There > >>> are no problems with disk images formatted with a block size on 4096 > >>> bytes. Anyway, I don't know if this is a coincidence. > >>> > >>> Do you think this could be the origin of the problem? If so, how can I > >>> solve it? > >>> In the links posted by Vijay someone suggests to start the VM with cache > >>> != > >>> none but this will prevent live migration, AFAIK. > >>> Another solution may be to recreate the volume backing it with XFS > >>> partitions formatted with a different block size (smaller? 1024 bytes?), > >>> this would be a painful option, but if this will solve the problem, I go > >>> for it. > >>> > >> > >> A lower sector size (512) for xfs has been observed to be useful in > >> overcoming this problem. > >> > >> Another solution might be to use logical_block_size=4096 option as > >> referred here [1]. > >> > >> -Vijay > >> > >> [1] https://bugzilla.redhat.com/show_bug.cgi?id=997839#c7 > >> > >> > > > > > > _______________________________________________ Gluster-users mailing list Gluster-users@xxxxxxxxxxx http://supercolony.gluster.org/mailman/listinfo/gluster-users
