[lug] LVM and disk failure

[Dan Ferris]

Your data goes bye bye.

LVM isn't for fault tolerance or redundancy, it's just a storage 
abstraction layer.  If you want fault tolerance then you put RAID 
devices into an LVM.  Just as RAID isn't designed to be expanded or resized.

I use LVM at work all the time and it saves me a large amount of grief 
with the amount of data that we have.

I don't know about evms, never used it.


Dan

Daniel Webb wrote:

>I've been Googling for the answer to this and failing, so:
>
>What happens when you have a 2-disk LVM volume group and disk 1 fails?
>Obviously this will depend on the filesystem you put on top of the volume,
>right?  So which filesystems will recover gracefully if you chop them in half
>like that?
>
>It's a little disturbing that in all the documentation I've read on LVM this
>is never mentioned, and yet it seems to destroy the main purpose of lvm: to be
>able to add and remove disks to a volume easily.  Each physical volume you add
>makes it that much more likely that you'll lose the whole thing.  Sure, you
>can put it on top of RAID, but now you lost your size flexibility because RAID
>isn't so easy to resize (or is it?).  The snapshots feature is nice, that's
>all I'll use it for until I find a satisfactory answer to this question.
>
>I also was checking out evms and it looks very interesting.  Any impressions
>from those who have used it?  Is it stable/reliable?  I didn't see anything in
>their docs either about recovering when one disk in a volume fails.
>
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