[Novalug] LVM query

Jon LaBadie novalugml@jgcomp.com
Mon Jul 19 17:32:35 EDT 2010


On Mon, Jul 19, 2010 at 09:25:44PM +0000, Jeff Stoner wrote:
> On Mon, 19 Jul 2010, Jon LaBadie wrote:
> 
> >Of the 4, two are internal, the other pair external
> >drives connected by USB.  I was planning on pooling
> >the internal pair and the external pair into two
> >volume groups.  But then I thought, why not a single
> >large VG?
> 
> /me runs away and hides
> 
> >The reason I'm hesitant to do a single group is
> >the external USB drives stop spinning after a period
> >of inactivity.  Then they are slow to reconnect.
> >Is that likely to cause problems with a single
> >large file system spanning the 4 drives when one
> >might not be available immediately?
> 
> I, honestly, would not use USB drives in any kind of software RAID
> or LVM configuration. My mantra has always been "USB drives are TAS
> (temporary attached storage), use them to transport data between
> systems when you can't use the network or as independent backup
> units."
> 
> You can try this if you want but one thing you may have to ensure is
> a consistent naming of the USB devices. Disk 1 may be /dev/sdh1 and
> disk 2 /dev/sdg1 one day but reboot and disk 1 may become /dev/sdg1
> and disk 2 /dev/sdh1 (flip-flop.) If you've built volumes using
> those device names, you may very well be screwed.
> 
> Dambit...now I'm curious. I'll have to try this and see what happens.
> 
In a previous incarnation, the same machine with the same USB drives
(plus part of one internal IDE drive) were used for backups.  There
I assured consistant naming/mounting by using UUIDs in the fstab.

But I see your point with LVMs.  What name will be used when creating
the pv's and adding them to the vg.  That will have to be consistant,
but how?

jon
-- 
Jon H. LaBadie                  novalugml@jgcomp.com
 JG Computing
 12027 Creekbend Drive		(703) 787-0884
 Reston, VA  20194		(703) 787-0922 (fax)



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