[CentOS] Re: Moving from RAID 0 to LVM RAID?

Fri Mar 7 15:08:09 UTC 2008
Toby Bluhm <tkb at MidwestInstruments.com>

Michael Simpson wrote:
> On 3/7/08, Scott Silva <ssilva at sgvwater.com> wrote:
>> on 3-6-2008 3:58 PM Scott R. Ehrlich spake the following:
>>> So I've learned a valuable RAID 0 lesson, and it fortunately was not a
>>> major catastrophy.  I got lucky, and had a workable-enough backup on
>>> tape to make the user who needed some data happy.
>>> Now, from the OS side, LVM is an option.   Say the RAID controller only
>>> allows hardware striping or mirroring for logical volumes, but I want to
>>> use more than two disks, and I don't want the RAID 0 problem again.
>>> When I get a replacement disk and build the system from the ground up
>>> again, I could, conceivably, use hardware RAID 1 for the OS on two
>>> disks, and CentOS 5 64-bit's LVM for software RAID 5 (or maybe 1+0 if
>>> available) on the remaining for 4 disks, maybe 3 disks as active and the
>>> 4th as a hot spare?
> Hi there,
> Minor point:
> Rather than go for a RAID 5 with a hot spare you are better off going
> for a RAID 6 array using the 4 discs if your hardware supports it.

sw raid supports raid 6. Another plus for sw raid is that it's hardware 
agnostic - doesn't care about controller make, brand, chipset, firmware, 

> If your RAID 5 has a disk failure then has another whilst it is
> rebuilding using the hot spare then your data is b0rked whereas with
> RAID 6 you can tolerate 2 disk failures and still access the data.
> You lose the same amount of capacity that you would have with the RAID
> 5 + hot spare set up that you are considering.
> mike

Toby Bluhm
Alltech Medical Systems America, Inc.
30825 Aurora Road Suite 100
Solon Ohio 44139