Re: [Xen-users] iSCSI vs NFS

[Grant McWilliams <grantmasterflash@xxxxxxxxx>]

On Tue, Feb 2, 2010 at 6:36 AM, Jeff Sturm <jeff.sturm@xxxxxxxxxx> wrote:

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-
> bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Andy Pace
> Sent: Monday, February 01, 2010 11:57 PM
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-users] iSCSI vs NFS
>
> What are the pro's and cons to each? From my research, iSCSI seems the
way to go
> here, but all the SAN/NAS vendor's I've spoken with live and die
*NFS*, which I've had
> some serious issues with in the past in so far as scalability and
performance...

Those don't have to be mutually exclusive.  From block storage you can
easily carve out some filesystems that you export as NFS.  And if you
really do have hundreds of VM's, I doubt you're going to do this on a
single SAN appliance unless I/O is *really* light.

For what it's worth, my money's on AoE rather than iSCSI.  Fast, simple,
extremely easy to setup and manage.  I prefer to run the block protocols
on dom0 hosts and export the block devices to domU's (phy:).  Tests show
this yields better throughput.

-Jeff

"Tests show". Famous last words...  I've been throwing around a lot of ideas in this same vein. I currently have 42 VMs running off the same disk in a classroom environment. Things are fine until everyone starts installing software or formatting their disks at the same time.

From the hearsay that I've heard AoE is the fastest network block storage but it's still hard to beat NFS. The problem comes about when you want more than one VM to access a storage device and then performance goes in the toilet because the cluster FS's are very slow. I however, don't make decisions based on hearsay so in the coming months I'll be testing all combinations of NFS, iSCSI, AoE, with GFS and OCFS and any other possibility I can find in common kernels. I'll be comparing these to the speeds of local disk access via ext3 to see how much of a hit (or advantage?) we take by moving storage out of box. Of course to do fast migration the storage has to be somewhere else...

Once testing is done I'll be posting the numbers. It's amazing how little benchmarking takes place. I did extensive tests on LVM vs disk files and have still not seen any other numbers on this. Oh well, I guess that will be my contribution.


Grant McWilliams

Some people, when confronted with a problem, think "I know, I'll use Windows." 
Now they have two problems.


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