topic Re: Striping existing logical volume in Operating System - HP-UX

Striping existing logical volume

Kevin O'Donovan — Tue, 05 Jul 2005 04:05:40 GMT

Hi,

I need to stripe a logical volume (28000MB lvol) on a server, and would like to avoid any downtime if possible.

What I was thinking of doing is to
- create a new striped logical volume,
- mirroring the old lvol and new lvol,
- then splitting the mirror leaving the new lvol as the one in use.

I don't know if you can mirror a non-striped lvol to a striped lvol though, is that possible?

Is there another better way of doing it?

tia,
Kevin.

Re: Striping existing logical volume

Bernhard Mueller — Tue, 05 Jul 2005 04:21:12 GMT

Kevin,

you cannot mirror lvol1 to lovl2, you can only setup a mirror for lvol1 on disk1 and disk2 e.g.

next, you cannot mirror *and* stripe with LVM. You can only use "distributed-extents" policy. this requires you setup the VG with the smallest possible PE size to actually achieve a striping effect (i.e. better performance). With most disks up to 73 GB you can use a PE size a 2MB, with 146GB disks you need 4MB PEs size otherwise you could not use the entire disks due to max PE per PV limits....

next you cannot change the PE size of an existing VG...

so most likely you will prefer a downtime I guess.

Regards,
Bernhard

Re: Striping existing logical volume

Christian Marquardt_1 — Tue, 05 Jul 2005 05:57:22 GMT

Hi Kevin,
I think I've the same problem.
I have to put rawdevices from one disk to striped over to disks.
I've a oracle database storing it's datafiles in rawdevices. The rlvols are stored on one disk only so there is a very bad performance.
Now I'll increase the number of disks und stripe the lvols.
To do this I've to drop the rawdevices and recreate new striped raws over all disks.
Naturaly this will destroy the datafile. Because of that I've to restore the database from backup after recreating the rawdevices.
I dont know if it is a good way with an 28 GB lvol.

kind regards
Christian