[Gluster-users] "Granular locking" - does this need to be enabled in 3.3.0 ?

Jake Grimmett jog at mrc-lmb.cam.ac.uk
Mon Jul 9 15:23:11 UTC 2012

Hi Fernando / Christian,

Many thanks for getting back to me.

Slow writes are acceptable; most of our VM's are small web servers with 
low traffic. My aim is to have a fully self-contained two server KVM 
cluster with live migration, no external storage and the ability to 
reboot either node with zero VM downtime.  We seem to be "almost there", 
bar a hiccup when the self-heal is in progress and some minor grumbles 
from sanlock (which might be fixed by the new sanlock in RHEL 6.3)

Incidentally, the logs shows a "diff" self heal on a node reboot:

[2012-07-09 16:04:06.743512] I 
0-gluster-rep-replicate-0: diff self-heal on /box1-clone2.img: 
completed. (16 blocks of 16974 were different (0.09%))

So, does this log show "Granular locking" occurring, or does it just 
happen transparently when a file exceeds a certain size?

many thanks


On 07/09/2012 04:01 PM, Fernando Frediani (Qube) wrote:
> Jake,
> I haven’t had a chanced to test with my KVM cluster yet but it should be
> a default things from 3.3.
> Just be in mind that running Virtual Machines is NOT a supported things
> for Redhat Storage server according to Redhat Sales people. They said
> towards the end of the year. As you might have observed performance
> specially for write isn’t any near fantastic.
> Fernando
> *From:*gluster-users-bounces at gluster.org
> [mailto:gluster-users-bounces at gluster.org] *On Behalf Of *Christian Wittwer
> *Sent:* 09 July 2012 15:51
> *To:* Jake Grimmett
> *Cc:* gluster-users at gluster.org
> *Subject:* Re: [Gluster-users] "Granular locking" - does this need to be
> enabled in 3.3.0 ?
> Hi Jake
> I can confirm exact the same behaviour with gluster 3.3.0 on Ubuntu
> 12.04. During the self-heal process the VM gets 100% I/O wait and is locked.
> After the self-heal the root filesystem was read-only which forced me to
> do a reboot and fsck.
> Cheers,
> Christian
> 2012/7/9 Jake Grimmett <jog at mrc-lmb.cam.ac.uk
> <mailto:jog at mrc-lmb.cam.ac.uk>>
> Dear All,
> I have a pair of Scientific Linux 6.2 servers, acting as KVM
> virtualisation hosts for ~30 VM's. The VM images are stored in a
> replicated gluster volume shared between the two servers. Live migration
> works fine, and the sanlock prevents me from (stupidly) starting the
> same VM on both machines. Each server has 10GB ethernet and a 10 disk
> RAID5 array.
> If I migrate all the VM's to server #1 and shutdown server #2, all works
> perfectly with no interruption. When I restart server #2, the VM's
> freeze while the self-heal process is running - and this healing can
> take a long time.
> I'm not sure if "Granular Locking" is on. It's listed as a "technology
> preview" in the Redhat Storage server 2 notes - do I need to do anything
> to enable it?
> i.e. set "cluster.data-self-heal-algorithm" to diff ?
> or edit "cluster.self-heal-window-size" ?
> any tips from other people doing similar much appreciated!
> Many thanks,
> Jake
> jog <---at---> mrc-lmb.cam.ac.uk <http://mrc-lmb.cam.ac.uk>
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Dr Jake Grimmett
Head Of Scientific Computing
MRC Laboratory of Molecular Biology
Hills Road, Cambridge, CB2 0QH, UK.
Phone 01223 402219
Mobile 0776 9886539

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