software raid question

fakie_flip · 10-29-2007, 09:29 PM

How can linux software raid be setup with raid level 0 if the installer of a linux distro does not support raid in the partitioner?

acid_kewpie · 10-30-2007, 02:32 PM

there's no point using raid 0, use LVM instead for the same result but in a much much friendlier and more flexible manner.

if you really did need to set it up, you could create the raid using a rescue disk beforehand and just pick up the drive as you install. assuming it recognises the existing one.

fakie_flip · 10-30-2007, 04:44 PM

Quote:

Originally Posted by acid_kewpie

there's no point using raid 0, use LVM instead for the same result but in a much much friendlier and more flexible manner.

if you really did need to set it up, you could create the raid using a rescue disk beforehand and just pick up the drive as you install. assuming it recognises the existing one.

Do you mean install on /dev/md* devices? Do most installers see those? Do you know of a good guide for the LVM setup that you are talking about? Why is raid usually used in conjunction with LVM if LVM can do striping (the same thing as raid)?

acid_kewpie · 10-30-2007, 05:38 PM

most installers now cover both lvm and raid creation. i've only really installed fedora / redhat in the lat year or so, but they've certainly done a great job.

and raid isn't striping. striping is just a small part of the point of raid, parity is the other side, i.e. fault tolerance. raid 0 / lvm do not provide any fault tolerance at all, raid 1 provides *only* fault tolerance, no striping, and onwards from there are variously merited combinations, e.g. raid 5.

fakie_flip · 10-30-2007, 11:18 PM

EDIT: sorry, double post

fakie_flip · 11-28-2007, 11:36 PM

Quote:

Originally Posted by acid_kewpie

there's no point using raid 0, use LVM instead for the same result but in a much much friendlier and more flexible manner.

Why is LVM a much more friendlier and flexible manner and why is it used in combination with RAID if it does the same thing?

lazlow · 11-29-2007, 01:29 AM

Not on point but:

LVM is fine, until it has a problem. If something goes wrong it adds another layer to figure out what is wrong. If you try to move a LVM volume from one install to another (physically) you have to change the name of the volume. The trouble with that is that you cannot mount two volumes with the same name(standard default) at the same time, but you have to mount the volume to change the name (live cd is the way out). You also cannot see(as in use) a lvm from most other OSs (windows). It does allow you to seamlessly span drives but most(not all) of that can be handled by using mount points on a "master" drive.

A lot of us avoid LVMs like the plague due to the risk/reward ratio. Once an LVM burns you good it is tough to forget.

Good Luck
Lazlow