Hi Yaniv, Thanks for your detailed reply, it's very much appreciated.
> On 5 Jan 2018, at 8:34 pm, Yaniv Kaul <[email protected]> wrote: > > Indeed, greenfield deployment has its advantages. > > The down side to that is juggling iSCSI LUNs, I'll have to migrate VMs on > XenServer off one LUN at a time, remove that LUN from XenServer and add it to > oVirt as new storage, and continue - but if it's what has to be done, we'll > do it. > > The migration of VMs has three parts: > - VM configuration data (from name to number of CPUs, memory, etc.) That's not too much of an issue for us, we have a pretty standard set of configuration for performance / sizing. > - Data - the disks themselves. This is the big one, for most hosts at least the data is on a dedicated logical volume, for example if it's postgresql, it would be LUKS on top of a logical volume for /var/lib/pgsql etc.... > - Adjusting VM internal data (paths, boot kernel, grub?, etc.) Everything is currently PVHVM which uses standard grub2, you could literally dd any one of our VMs to a physical disk and boot it in any x86/64 machine. > The first item could be automated. Unfortunately, it was a bit of a challenge > to find a common automation platform. For example, we have great Ansible > support, which I could not find for XenServer (but[1], which may be a bit > limited). Perhaps if there aren't too many VMs, this could be done manually. > If you use Foreman, btw, then it could probably be used for both to provision? > The 2nd - data movement could be done in at least two-three ways: > 1. Copy using 'dd' from LUN/LV/raw/? to a raw volume in oVirt. > 2. (My preferred option), copy using 'dd' from LUN/LV/raw and upload using > the oVirt upload API (example in Python[2]). I think that's an easy to > implement option and provides the flexibility to copy from pretty much any > source to oVirt. A key thing here would be how quickly the oVirt API can ingest the data, our storage LUNs are 100% SSD each LUN can easily provide at least 1000MB/s and around 2M 4k write IOP/s and 2-4M 4k read IOP/s so we always find hypervisors disk virtualisation mechanisms to be the bottleneck - but adding an API to the mix, especially one that is single threaded (if that does the data stream processing) could be a big performance problem. > 3. There are ways to convert XVA to qcow2 - I saw some references on the > Internet, never tried any. This is something I was thinking of potentially doing, I can actually export each VM as an OVF/OVA package - since that's very standard I'm assuming oVirt can likely import them and convert to qcow2 or raw/LVM? > > As for the last item, I'm really not sure what changes are needed, if at all. > I don't know the disk convention, for example (/dev/sd* for SCSI disk -> > virtio-scsi, but are there are other device types?) Xen's virtual disks are all /dev/xvd[a-z] Thankfully, we partition everything as LVM and partitions (other than boot I think) are mounted as such. > > I'd be happy to help with any adjustment needed for the Python script below. Very much appreciated, when I get to the point where I'm happy with the basic architectural design and POC deployment of oVirt - that's when I'll be testing importing VMs / data in various ways and have made note of these scripts. > > Y. > > [1] http://docs.ansible.com/ansible/latest/xenserver_facts_module.html > <http://docs.ansible.com/ansible/latest/xenserver_facts_module.html> > [2] > https://github.com/oVirt/ovirt-engine-sdk/blob/master/sdk/examples/upload_disk.py > > <https://github.com/oVirt/ovirt-engine-sdk/blob/master/sdk/examples/upload_disk.py> >
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