LVM + RAID follow up

[warlord at MIT.EDU (Derek Atkins)]

Quoting Tom Metro <blu at vl.com>:

> RAID-1 is a no brainer, but what I wonder about is the use of higher 
> order RAID or LVM layered on top of non-RAID volumes in the case of 
> "budget" systems where you don't have backups (or at least frequent 
> backups).

It depends on your usage.  What are you storing on the system, and
what kind of problems are you trying to offset by using RAID?

> It's been raised on this list before, and from that and other 
> sources, my understanding is that LVM can make data recovery a lot 
> more difficult if one of the underlying drives fails. This is 
> probably why LVM is typically layered on top of RAID sets.

True.  LVM is another way to accomplish RAID0, so I'd question
whether you want a true RAID-0 vs. just using LVM.

> In a more enterprise environment, recovery isn't really an issue. You 
> create frequent backups (or continuous mirrors) and test them. But 
> for a home MythTV Backend, I can see scenarios where you might chain 
> a couple of large drives via LVM and no RAID to go for maximum space, 
> and risk not having backups, yet would much rather be able to recover 
> the surviving data from the LVM group if a drive fails.

For myth video I'd just mount the disks separately and configure Myth
to load-share the space across the mountpoints.  This way if you lose
a drive you only lose the videos on that drive and not ALL your videos.

I'd not use RAID for that..  I WOULD use RAID for longer-term storage,
like a backup server or a video/audio jukebox or longer-term storage of
data that I don't want to lose.

>  -Tom

-derek

-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
       warlord at MIT.EDU                        PGP key available


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