[Gluster-users] volume sizes

Raghavendra G raghavendra at gluster.com
Wed Dec 30 15:40:23 UTC 2009

Hi Anthony,

On Wed, Dec 30, 2009 at 6:30 PM, Anthony Goddard <agoddard at mbl.edu> wrote:

> Hi Tejas,
> Thanks for the advice. I will be using RAID as well as gluster replication
> I think.. as we'll only need to sacrifice 1 drive per raid set to add a bit
> of extra redundancy.
> The rebuild happens at the first access of a file, does this mean that the
> entire brick/node is rebuilt upon an initial file access?

No, only the file which is accessed is rebuilt. That is the reason we
recursively access all the files using 'ls -laR' on mount point.

> I think this is what I've seen from using gluster previously. If this is
> the case, it would rebuild the entire volume which could span many raid
> volumes or even machines, is this correct? If this is the case, then the
> underlying disk wouldn't have any effect at all, but if it's spanned over
> multiple machines and it only needs to rebuild one machine (or multiple
> volumes on one machine) it only needs to rebuild one volume.
> I don't know if that made any sense.. haha.. but if it did, any insights
> into whether the size of the volumes (aside from RAID rebuilds) will have a
> positive effect on glusters rebuild operations?
> Cheers,
> Ant.
> On Dec 30, 2009, at 2:56 AM, Tejas N. Bhise wrote:
> > Anthony,
> >
> > Gluster can take the smaller ( 6TB ) volumes and aggregate them into a
> large Gluster volume ( as seen from the clients ). So that takes care of
> managebility on the client side of things. On the server side, once you make
> those smaller 6 TB volumes, you will depend on RAID to rebuild the disk
> behind it, so its good to have a smaller partition. Since you are using RAID
> and not Gluster replication, it might just make sense to have smaller RAID
> partitions.
> >
> > If instead you were using Gluster replication and resulting recovery, it
> would happen at first access of the file and the size of the Gluster volume
> or the backend native FS volume or the RAID ( or raw ) partition behind it
> would not be much of a consideration.
> >
> > Regards,
> > Tejas.
> >
> > ----- Original Message -----
> > From: "Anthony Goddard" <agoddard at mbl.edu>
> > To: gluster-users at gluster.org
> > Sent: Wednesday, December 30, 2009 3:24:35 AM GMT +05:30 Chennai,
> Kolkata, Mumbai, New Delhi
> > Subject: [Gluster-users] volume sizes
> >
> > First post!
> > We're looking at setting up 6x 24 bay storage servers (36TB of JBOD
> storage per node) and running glusterFS over this cluster.
> > We have RAID cards on these boxes and are trying to decide what the best
> size of each volume should be, for example if we present the OS's (and
> gluster) with six 36TB volumes, I imagine rebuilding one node would take a
> long time, and there may be other performance implications of this. On the
> other hand, if we present gluster / the OS's with 6x 6TB volumes on each
> node, we might have more trouble in managing a larger number of volumes.
> >
> > My gut tells me a lot of small (if you can call 6TB small) volumes will
> be lower risk and offer faster rebuilds from a failure, though I don't know
> what the pros and cons of these two approaches might be.
> >
> > Any advice would be much appreciated!
> >
> >
> > Cheers,
> > Anthony
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Raghavendra G

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