Re: [Xen-users] Converting AND shrinking domU

["Nick Couchman" <Nick.Couchman@xxxxxxxxx>]

> 
> 
> ïOCFS2 does not allow sparse disks? I've never heard of that. I have
had
> tickets open with novell and they have never said it's not
supported.
> I've emailed this list saying we're using ocfs2 and sparse files and
> nobody has raised any flags before (which could be understandable
being
> a mailing list).

Perhaps OCFS2 on SLES11 does support sparse files.  On SLES10, OCFS2
definitely does not support sparse files - if you try to create a sparse
disk file, either via virt-manager or using a command like "dd
if=/dev/zero of=disk0 bs=1G seek=10", it actually takes up 10 GB of
space on the filesystem and disk, not the 10MB or so that you would
expect from a sparse disk file.

> 
> We are currently doing sparse files on ocfs2. It was going fine for
> about a year, then we started having problems with ocfs2 becoming
> corrupted. 

I'm using SLES10 and I do not have any trouble with OCFS2 corruption. 
Not quite as new a version of Xen, but it's rock solid.

> 
> I don't know if the SAN supported thin provisioning, but I'm also
not
> sure what you mean. Can you elaborate a little? 
> 

Thin provisioning is a similar concept to sparse disks, but at the LUN
level.  It basically allows you to create a 100GB LUN, for example, but
only have it consume the space on your physical disks that is actually
used on the volume.  This allows you to over-allocate SAN disk space,
using only what you're currently storing but allowing for future growth
without the need to expand the LUN every time you want to grow.  We use
Compellent for our SAN, which features thin provisioning, and I'm also
experimenting with using OpenSolaris + ZFS + COMSTAR in a shared storage
role, and ZFS supports thin provisioning of ZFS volumes.

Obviously thin provisioning (and sparse files, for that matter) come
with some risk: if you're over-allocating storage space, you risk
filling up your physical disks completely, which is never a good thing. 
But, if you manage your environment properly, you'll have enough warning
and you'll be able to add more storage space before you hit that
threshold.

-Nick


--------
This e-mail may contain confidential and privileged material for the sole use 
of the intended recipient.  If this email is not intended for you, or you are 
not responsible for the delivery of this message to the intended recipient, 
please note that this message may contain SEAKR Engineering (SEAKR) 
Privileged/Proprietary Information.  In such a case, you are strictly 
prohibited from downloading, photocopying, distributing or otherwise using this 
message, its contents or attachments in any way.  If you have received this 
message in error, please notify us immediately by replying to this e-mail and 
delete the message from your mailbox.  Information contained in this message 
that does not relate to the business of SEAKR is neither endorsed by nor 
attributable to SEAKR.

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users