[clue-tech] Linux LVM corruption?

[Keith Hellman]

On Tue, Jul 08, 2008 at 01:52:20PM -0600, Jim Ockers wrote:
> 1. Is an LVM any more or less likely to become corrupt than just a normal
> partition table?  My inkling is no.
Mine too, but I've never run a system in "industrial conditions".
 
> 2. If we issue a filesystem resize sequence of events/commands and the
> power is lost at a bad moment, how likely is it that the failure would be
> unrecoverable?  I have no idea.
> 
> 3. How often does the LVM metadata turn into garbage?  My inkling is not
> very often but I'd like to hear some stories.
 
I don't have explicit experience with LVM under these conditions, but I
have been in your shoes before:  trying to determine if technology X is
good choice for a system in a high-reliability use-case and an
unfriendly environment.

I would test ext3 resizing 10, 20, 30, 100 times (you pick how much
time you have), and pull the power at some random time during the
processing.  If fsck can recover the filesystem, I think it can probably
be made to work.

I have used LVM for a long time (I think I did a CLUE talk on it once a
LONG, LONG, time ago), specifically so that I can resize my partitions
at will.  The LVM processing never takes long, so it seems to me that
the resize operation is probabilistically more likely to hit the power
drop failure.  That's where the real testing efforts should be.

Confirming that the LVM system can survive a power drop during its meta
data updates probably requires looking into the source and its design.

Just my 2c.
-- 
Keith Hellman                             #include <disclaimer.h>
khellman at mcprogramming.com                from disclaimer import standard
khellman at mines.edu
                                   -*-                                    
                    public key @ pgp.mit.edu 9FCF40FD 
    Y!M: mcprogramming                           AIM/ICQ: 485403897       
                     gtalk: jabber at mcprogramming.com                      
                                   -*-                                    

"Whenever I hear anyone arguing for slavery, I feel a strong
impulse to see it tried on him personally."

-- Abraham Lincoln
   http://columbia.thefreedictionary.com/Lincoln,+Abraham
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: Digital signature
Url : http://cluedenver.org/pipermail/clue-tech/attachments/20080711/210a0de5/attachment.bin