topic Re: Mirror 500GB, then un-mirror in Operating System - Linux

Mirror 500GB, then un-mirror

Basheer_2 — Tue, 18 Oct 2005 12:56:35 GMT

Hello
Linux AS Ver 3.5
current file sys is lvm = 500GB
need to mirror to another disk
then break the mirror.
Anyone has done it in Linux.
can you explain how to do this.

Re: Mirror 500GB, then un-mirror

Ivan Ferreira — Tue, 18 Oct 2005 13:52:55 GMT

Isn't more easy just copy the data?

Why mirror then unmirror that disk only?

Re: Mirror 500GB, then un-mirror

Basheer_2 — Tue, 18 Oct 2005 14:07:33 GMT

Thanks

In my Experience (HPUX), Mirroring is minimum 3 Times faster than Copying.

Re: Mirror 500GB, then un-mirror

Ivan Ferreira — Tue, 18 Oct 2005 14:52:49 GMT

Ok, but you will enter in too much complications. The time you spend configuring the raid device will match the time you need to copy the files.

cd /mirror_mounted_device
use star -c -xdev -C . | xtar -xp

to copy the files, you will see that is very fast.

Using raid + LVM in linux is a little more difficult in linux, because mirroring is not provided by LVM, is provided by md devices.

Anyway, you can see the Software RAID and LVM HOWTO.

Re: Mirror 500GB, then un-mirror

Basheer_2 — Tue, 18 Oct 2005 14:55:52 GMT

Thanks Ivan

I am not Using RAID, trying to do it only thru LVM.

Re: Mirror 500GB, then un-mirror

Ivan Ferreira — Tue, 18 Oct 2005 15:25:57 GMT

LVM mirroring in HP-UX is more or less a RAID 1. So, to simulate that, you need SOFTWARE RAID + LVM, because LVM in linux does not provides the ability to map one logincal extend to two physical extends (number of copies).

Re: Mirror 500GB, then un-mirror

Craig Gilmore — Tue, 18 Oct 2005 23:05:24 GMT

There is a solution, but not until RHEL 4. There is no mirroring for LVM in RHEL 3. On RHEL 4 you can do exactly what you describe, as mirroring and snapshots are part of the LVM implementation.

Yes, you could go to the source for RHEL 4, grab the LVM and then on RHEL 3 replace the LVM source and build a new kernel... How much time do you want to spend?