Re: moving LVM logical volumes to new disks
Don Armstrong <don@debian.org> writes:
> On Wed, 12 Nov 2014, lee wrote:
>> what's the best way to move existing logical volumes or a whole volume
>> group to new disks?
>>
>> The target disks cannot be installed at the same time as the source
>> disks. I will have to make some sort of copy over the network to
>> another machine, remove the old disks, install the new disks and put the
>> copy in place.
>>
>> The LVs contain VMs. The VMs can be shut down during the migration.
>> It's not possible to make snapshots because the VG is full.
>>
>> New disks will be 6x1TB RAID-5, old ones are 2x74GB RAID-1 on a
>> ServeRaid 8k. No more than 6 discs can be installed at the same time.
>
> You can remove one of the RAID-1 drives, install 5 of the 1T drives, and
> start both raids in degraded mode temporarily. Once you've done that,
> add the new PVs to the VG, and pvmove.
>
> Alternatively, you can start with three drives in raid-5, and then grow
> the array out to the additional three drives, once you've done the
> migration, or have two different raid-5 arrays in the same vg.
>
> Alternatively, you can use an external enclosure to house the RAID1 or
> RAID5 temporarily. USB is slow, but workable.
Yes, I thought about something like this. I'm not sure whether I can
actually grow the RAID-5. I could create the new RAID-5 with 6 disks
and then remove one to run both arrays in degraded mode to copy things
over.
However, I currently have dom0 on a non-LVM partition, and I want to
make a single LVM partition from the new RIAD-5 with several LVs. The
largest LV will be for data. I want to have more room for VMs, too, and
I want to be able to increase the size of the existing LVs --- either in
the future or while I am at it.
I want to convert dom0 to a LV, and I'm not sure whether it's better to
re-install dom0 on LV or to copy and convert the existing one somehow.
I'm also not sure what limits copying with dd would introduce. I might
be better off making copies of everything over the network --- with the
added benefit of having a backup which I currently don't have --- and
then copying everything back with something like 'cp -a'. Using 'cp -a'
worked fine in the past, and I was able to boot a rescue system to
install grub.
I've never done that with VMs in LVs, though. When I boot a rescue
system, can I still install grub in each of the LVs?
I also have a spare 1TB disk which I can use in another machine
to make the backups to.
--
Again we must be afraid of speaking of daemons for fear that daemons
might swallow us. Finally, this fear has become reasonable.
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