Tom Van Overbek wrote:
> On Fri, 09 Apr 2004 22:02:38 +0000, Simon Marchese wrote:
>
>
>>Tom Van Overbeke wrote:
>>
>>>Hi,
>>>
>>>I have a question about splitlvcopy and chlvcopy:
>>>
>>>is it correct that splitlvcopy is used to create an independent logical
>>>volume based on an existing mirror copy of a logical volume ?
>>>actually a conversion of a mirrored copy to a new logical volume.
>>>this logical volume has no links anymore with the original logical volume,
>>>except the fact that the filesystem on it has the same label as the old one.
>>>and there is no way of reusing the new logical volume as a mirror copy of
>>>the original logical volume
>>>
>>>and chlvcopy is used to temporarily break a mirror, to allow one to take a
>>>backup of data, and afterwards the copy can be re-attached to the original
>>>logical volume and resync'ed.
>>>
>>>the difference is important to me, because i plan (while doing a migration
>>>of data between 2 san's) to do this:
>>>
>>>a logical volume that is mirrorred on 2 disks, will be cut via the
>>>splitlvcopy command. the copy on the second disk will become an independent
>>>logical volume. this second disk will be disconnected (via san tools) from
>>>the server (and be kept as a 'online' backup).
>>>then the original logical volume will be sync'ed to another new disk.
>>>if the original logical volume becomes unavailable (because the first disk
>>>is corrupt or sth), we will re-connect the second disk to the server, mark
>>>the physical disk as active (chpv -va) and be able to use the 'new' logical
>>>volume that contains the same data as the original one.
>>>
>>>
>>>everythone still with me ?
>>>
>>>
>>>any input is appreciated.
>>>
>>>thx,
>>>tom.
>>>
>>>
>>
>>Yes, the difference is as you describe. However, all the names of the
>>LVs get changed (check the manpage and/or try it out). Therefore you
>>cannot just "use" them to replace the original ones. Worse, you will
>>actually have quorum issues as you have just removed half the volumes in
>>a VG. And when you try to use the "removed" disks you will also have
>>quorum issues, no matter how you do it.
>
>
>
> Hi Simon,
>
> Yes I am aware of the possible quorum issues but these shouldn't be
> critical, as there's always the possibility to varyon a volumegroup with
> the force option if need be, no ?
>
> regards,
>
> tom.
>

Sorry Tom, it's worse that that. There's the possibility that data
resync will go the wrong way and you won't know about it until after it
has happened.