[mythtv-users] Should I use LVM on this new raid?

Michael Heironimus mkh01 at earthlink.net
Sat Sep 22 21:19:09 UTC 2007

On Sat, Sep 22, 2007 at 02:16:04PM -0500, Brian Foddy wrote:
> As I see it, I can make the raid expandable as one /dev/sdb and then 
> partition it with fdisk or whatever just like a normal HD.
> Or I would tell the raid controller to limit the unit size to say 1TB,
> and it would then break my 2 drives up a /dev/sdb and /dev/sdc.
> Then attach a PV to each (or even smaller sections).

You could do it either way, it comes down to how you want to manage the
storage. I usually use one big volume and make the LVM partition as
large as possible. Other people prefer to make the LVM partitions only
as big as they need right now and add new partitions as needed.

> I've heard its more efficient to attach the LVM directly to the device
> and not partition so the stripe size match up better (64KB)??  I maybe
> be mangling the argument??

There are many things I'd look at before getting down to matching up
block sizes - a controller with a huge battery-backed writeback cache,
15k RPM U320 or fibre channel drives, etc... If your controller allows
you to add a disk to the array and create a new volume on the empty
space instead of expanding the existing volume then you'll be able to
use whole-disk devices. If it requires you to expand the volume then
you'll have to partition.

Michael Heironimus

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