[ovirt-users] Disaster Recovery Testing

[Fred Rolland]

Gary,

See this wiki page, it explains how to import storage domains :
http://www.ovirt.org/develop/release-management/features/storage/importstoragedomain/

Regards,

Fred

On Wed, Feb 15, 2017 at 10:15 PM, Nir Soffer <nsoffer at redhat.com> wrote:

> On Wed, Feb 15, 2017 at 9:30 PM, Gary Lloyd <g.lloyd at keele.ac.uk> wrote:
> > Hi Nir thanks for the guidance
> >
> > We started to use ovirt a good few years ago now (version 3.2).
> >
> > At the time iscsi multipath wasn't supported, so we made our own
> > modifications to vdsm and this worked well with direct lun.
> > We decided to go with direct lun in case things didn't work out with
> OVirt
> > and in that case we would go back to using vanilla kvm / virt-manager.
> >
> > At the time I don't believe that you could import iscsi data domains that
> > had already been configured into a different installation, so we
> replicated
> > each raw VM volume using the SAN to another server room for DR purposes.
> > We use Dell Equallogic and there is a documented limitation of 1024 iscsi
> > connections and 256 volume replications. This isn't a problem at the
> moment,
> > but the more VMs that we have the more conscious I am about us reaching
> > those limits (we have around 300 VMs at the moment and we have a vdsm
> hook
> > that closes off iscsi connections if a vm is migrated /powered off).
> >
> > Moving to storage domains keeps the number of iscsi connections /
> replicated
> > volumes down and we won't need to make custom changes to vdsm when we
> > upgrade.
> > We can then use the SAN to replicate the storage domains to another data
> > centre and bring that online with a different install of OVirt (we will
> have
> > to use these arrays for at least the next 3 years).
> >
> > I didn't realise that each storage domain contained the configuration
> > details/metadata for the VMs.
> > This to me is an extra win as we can recover VMs faster than we can now
> if
> > we have to move them to a different data centre in the event of a
> disaster.
> >
> >
> > Are there any maximum size / vm limits or recommendations for each
> storage
> > domain ?
>
> The recommended limit in rhel 6 was 350 lvs per storage domain. We believe
> this
> limit is not correct for rhel 7 and recent ovirt versions. We are
> testing currently
> 1000 lvs per storage domain, but we did not finish testing yet, so I
> cannot say
> what is the recommended limit yet.
>
> Preallocated disk has one lv, if you have thin disk, you have one lv
> per snapshot.
>
> There is no practical limit to the size of a storage domain.
>
> > Does Ovirt support moving VM's between different storage domain type e.g.
> > ISCSI to gluster ?
>
> Sure, you can move vm disks from any storage domain to any storage domain
> (except ceph).
>
> >
> >
> > Many Thanks
> >
> > Gary Lloyd
> > ________________________________________________
> > I.T. Systems:Keele University
> > Finance & IT Directorate
> > Keele:Staffs:IC1 Building:ST5 5NB:UK
> > +44 1782 733063
> > ________________________________________________
> >
> > On 15 February 2017 at 18:56, Nir Soffer <nsoffer at redhat.com> wrote:
> >>
> >> On Wed, Feb 15, 2017 at 2:32 PM, Gary Lloyd <g.lloyd at keele.ac.uk>
> wrote:
> >> > Hi
> >> >
> >> > We currently use direct lun for our virtual machines and I would like
> to
> >> > move away from doing this and move onto storage domains.
> >> >
> >> > At the moment we are using an ISCSI SAN and we use on replicas created
> >> > on
> >> > the SAN for disaster recovery.
> >> >
> >> > As a test I thought I would replicate an existing storage domain's
> >> > volume
> >> > (via the SAN) and try to mount again as a separate storage domain
> (This
> >> > is
> >> > with ovirt 4.06 (cluster mode 3.6))
> >>
> >> Why do want to replicate a storage domain and connect to it?
> >>
> >> > I can log into the iscsi disk but then nothing gets listed under
> Storage
> >> > Name / Storage ID (VG Name)
> >> >
> >> >
> >> > Should this be possible or will it not work due the the uids being
> >> > identical
> >> > ?
> >>
> >> Connecting 2 storage domains with same uid will not work. You can use
> >> either
> >> the old or the new, but not both at the same time.
> >>
> >> Can you explain how replicating the storage domain volume is related to
> >> moving from direct luns to storage domains?
> >>
> >> If you want to move from direct lun to storage domain, you need to
> create
> >> a new disk on the storage domain, and copy the direct lun data to the
> new
> >> disk.
> >>
> >> We don't support this yet, but you can copy manually like this:
> >>
> >> 1. Find the lv of the new disk
> >>
> >>     lvs -o name --select "{IU_<new-disk-uuid>} = lv_tags" vg-name
> >>
> >> 2. Activate the lv
> >>
> >>     lvchange -ay vg-name/lv-name
> >>
> >> 3. Copy the data from the lun
> >>
> >>     qemu-img convert -p -f raw -O raw -t none -T none
> >> /dev/mapper/xxxyyy /dev/vg-name/lv-name
> >>
> >> 4. Deactivate the disk
> >>
> >>     lvchange -an vg-name/lv-name
> >>
> >> Nir
> >
> >
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