[ovirt-users] Fwd: Are there some general strategyhow to Iscsi strorage domain?

[Vered Volansky]

Backup of a whole storage domain is problematic with regards to the data consistency.
I would assume the important entities are specific VM disks and templates and you should try to backup the most important ones more frequently than others.
It would be more correct to take a live snapshot of a disk and then use dd or DRBD as you suggested, as frequently as you need. This also ensure the data consistency much better than a whole storage domain.

To better answer your question,  
What is the general use of your domains? What is the general number of disks you have there?
What percentage are the most important ones? Do you really want all of them backed-up? How often do you need the backup to take place?

Regards,
Vered

----- Original Message -----
> From: "Arman Khalatyan" <arm2arm at gmail.com>
> To: "users" <users at ovirt.org>
> Sent: Thursday, October 23, 2014 11:11:43 AM
> Subject: [ovirt-users] Fwd: Are there some general strategyhow to Iscsi strorage domain?
> 
> 
> ---------- Forwarded message ----------
> From: Arman Khalatyan < arm2arm at gmail.com >
> Date: Thu, Oct 23, 2014 at 10:11 AM
> Subject: Re: [ovirt-users] Are there some general strategyhow to Iscsi
> strorage domain?
> To: Trey Dockendorf < treydock at gmail.com >
> 
> 
> Thank you Trey for sharing your setup.
> I have also one test system with zvol exported with iscsi over 10G.
> Unfortunately the difference in performance of zfs over raid controller is
> huge, particularly where VM running mysql. I did not try HBAs yet, I have
> only LSI/Adaptec/Areca RaidControllers they dont have IT mode. Maybe that
> can be the reason.
> For sure always one need to find the sweet edge between performance and
> reliability.
> Just for comparison with yours I get on random IO:
> zvol/16Disks/Raid2/tgtd/iscsi/10G-> on VM multiple rsync - ~100-150MB/s,
> Same HW but disks with Areca RAID6 - 650MB/s stable even more in some cases.
> The best performance I got on FDR iser->
> 80% of bare metal performance: 1500MB/s but ovirt goes mad claiming that
> Network and Disk devices are saturated. My VM goes time by time to paused
> state.
> It is due to that the Ovirt treating all ib devices as 10Gbit cards(in terms
> of speed).:(
> 
> 
> 
> On Thu, Oct 23, 2014 at 8:30 AM, Trey Dockendorf < treydock at gmail.com >
> wrote:
> 
> 
> 
> 
> Not sure if it's a solution for you, but ZFS. My domains are all ZFS (using
> ZFS on Linux in EL6.5) and my backup server receives incremental snapshots
> from primary storage which includes both NFS exports and iSCSI. ZFS makes
> creating block devices for iSCSI very easy, and they are included in
> snapshot replication. The replication is not HA but disaster recovery and
> off site.
> 
> I've hit 300MB/s using ZFS send over IPoIB on my DDR fabric, which isn't
> amazing but not terrible for an old DDR fabric.
> 
> ZFS is probably not an easy solution as requires rebuilding your storage, but
> maybe for future use or other readers it will give some useful ideas.
> 
> - Trey
> On Oct 22, 2014 11:56 AM, "Arman Khalatyan" < arm2arm at gmail.com > wrote:
> 
> 
> 
> Hi,
> I have 2x40TB domains each are exported with iser/iscsi with ib and 10Gb
> interfaces.
> For sure they are RAID6 storage little bit save on failure.
> But I was wondered if any way to backup those domains. particularly master
> one.
> 
> I was thinking somehow DRBD based replication, with lvm snapshots etc. But it
> looks like overkill.
> Will be nice somehow to deploy replicated/HA Master domain with ability to
> backp on tapes as well.
> 
> Any ideas are welcome.
> Thanks,
> Arman.
> 
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