[Gluster-users] Question about Volume Type when bricks are on SAN

[Mike Hanby]

So based on the suggestions from both you and Daniel many smaller LUNs should be better for performance and maintenance.

Question regarding LVM, do you use LVM to place all of the luns into a single volume group and ultimately a single logical volume / brick? Or does each LUN become it's own volume group and logical volume and brick?

Based on what you suggested regarding fsck on smaller file systems I suspect the latter, where you'd have many smaller bricks per server rather than a single large brick comprised of many luns in a single logical volume.

Thanks,

Mike

-----Original Message-----
From: gluster-users-bounces at gluster.org [mailto:gluster-users-bounces at gluster.org] On Behalf Of Craig Carl
Sent: Sunday, October 24, 2010 2:15 AM
To: Daniel Mons
Cc: gluster-users at gluster.org
Subject: Re: [Gluster-users] Question about Volume Type when bricks are on SAN

Another good reason to keep your LUN's small is the possibility of having to fsck the filesystem. Even on really fast disk it can take days to fsck a 16TB LUN. Gluster hides the multiple LUNs in a volume so you never have to deal with them, other than a bit more SAN management and more typing to setup a volume the first time there is no downside. 

Thanks, 

Craig 

--> 
Craig Carl 
Senior Systems Engineer 
Gluster 


From: "Daniel Mons" <daemons at kanuka.com.au> 
To: gluster-users at gluster.org 
Sent: Saturday, October 23, 2010 5:38:12 AM 
Subject: Re: [Gluster-users] Question about Volume Type when bricks are on SAN 

On Sat, Oct 23, 2010 at 5:22 AM, Mike Hanby <mhanby at uab.edu> wrote: 
> Each Gluster server has been allocated a single 9TB LUN (if it makes any sense to do so, I could have the SAN admin provide many smaller LUNs per server and use LVM to combine into single brick) 

Generally speaking you should LVM over many smaller LUNs. With 
multiport FC HBAs being the standard, you will get better performance 
as separate requests hit separate LUNs. Multiple LUNs mean multiple 
SCSI queues, which can reduce I/O latency substantially. 

We try to cap our LUNs at around 100GB. It does make for a lot of 
LUNs per server, but it's worth if for the performance gain. Talk to 
your storage admin and ask them what their recommendation is based on 
your vendor and their best practices. 

-Dan 
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