[ovirt-users] Manually moving disks from FC to iSCSI

[Elad Ben Aharon]

Hi,

I suggest another solution for you (which wasn't tested as a whole but much
simpler in my opinion).

 On the source environment:
- Create a local DC with a single local storage domain (let's call it sd1).
- Deactivate and detach the FC domain from the existing shared DC and
attach it to the local DC (From oVirt 4.1, attaching a shared storage
domain to a local data center is possible).
- Register FC domain VMs (from 'VM import' sub-tab under the FC domain).
- Move the disks from the FC domain to the local domain.
- Deactivate, detach and remove *without format* the local domain from the
source environment.
- Maintenance the host in the local data center (let's call it host1).

 On the destination environment:
- Add host1 to the destination environment and create a local data center
with this host and a new local domain.
- Import the existing local domain (sd1) to the local data center and
register its VMs.
- Deactivate and detach the iSCSI domain from the existing data center and
attach it to the local data center.
- Move all the disks from the local domain to the iSCSI domain.
- Deactivate and detach the iSCSI domain from the local data center, attach
and activate it in the shared data center and register its VMs.


Thanks,

ELAD BEN AHARON

SENIOR QUALITY ENGINEER

Red Hat Israel Ltd. <https://www.redhat.com/>

34 Jerusalem Road, Building A, 1st floor

Ra'anana, Israel 4350109

ebenahar at redhat.com    T: +972-9-7692007/8272007
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On Tue, Jul 11, 2017 at 4:14 PM, Gianluca Cecchi <gianluca.cecchi at gmail.com>
wrote:

>
>
> On Tue, Jul 11, 2017 at 2:59 PM, Gianluca Cecchi <
> gianluca.cecchi at gmail.com> wrote:
>
>> Hello,
>> I have a source oVirt environment with storage domain on FC
>> I have a destination oVirt environment with storage domain on iSCSI
>> The two environments can communicate only via the network of their
>> respective hypervisors.
>> The source environment, in particular, is almost isolated and I cannot
>> attach an export domain to it or something similar.
>> So I'm going to plan a direct move through dd of the disks of some VMs
>>
>> The workflow would be
>> On destination create a new VM with same config and same number of disks
>> of the same size of corresponding source ones.
>> Also I think same allocation policy (thin provision vs preallocated)
>> Using lvs -o+lv_tags I can detect the names of my origin and destination
>> LVs, corresponding to the disks
>> When a VM is powered down, the LV that maps the disk will be not open, so
>> I have to force its activation (both on source and on destination)
>>
>> lvchange --config 'global {use_lvmetad=0}' -ay vgname/lvname
>>
>> copy source disk with dd through network (I use gzip to limit network
>> usage basically...)
>> on src_host:
>> dd if=/dev/src_vg/src_lv bs=1024k | gzip | ssh dest_host "gunzip | dd
>> bs=1024k of=/dev/dest_vg/dest_lv"
>>
>> deactivate LVs on source and dest
>>
>> lvchange --config 'global {use_lvmetad=0}' -an vgname/lvname
>>
>> Try to power on the VM on destination
>>
>> Some questions:
>> - about overall workflow
>> - about dd flags, in particular if source disks are thin vs preallocated
>>
>> Thanks,
>> Gianluca
>>
>>
>
> Some further comments:
>
> - probably better/safe to use SPM hosts for lvchange commands both on
> source and target, as this imply metadata manipulation, correct?
> - when disks are preallocated, no problems, but when they are thin, I can
> be in this situation
>
> source disk defined as 90Gb disk and during time it has expanded up to 50Gb
> dest disk at the beginning just after creation will normally be of few GB
> (eg 4Gb), so the dd command will fail when fulll...
> Does this mean that it will be better to create dest disk as preallocated
> anyway or is it safe to run
> lvextend -L+50G dest_vg/dest_lv
> from command line?
> Will oVirt recognize its actual size or what?
>
>
>
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>
>
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