[lug] Server Partitioning Recommendation

[Hugh Brown]

dio2002 at indra.com wrote:
>>> B) help isolate the impacts of partition corruption.
>> I've never seen this, only whole-drive failure.  I'm sure it can happen,
>> though.  Keep revisioned backups such as rdiff-backup or regular offline
>> backups.  Don't span LVM across multiple physical devices.
> 
> I thought the whole purpose of LVM was so that you "can" span multiple
> physical devices.  Why would I not want to span LVM across physical
> devices?

IMO, the whole point of LVM is to be able to grow partitions as you need 
them (which doesn't preclude multiple physical devices, but it doesn't 
require it either).

One reason to be careful about spanning across physical devices is that 
if the LV is on multiple physical devices and one of them goes south, 
then you've lost the whole LV.  If you don't mind the risk of one of 
your PVs disappearing and taking with it all the LV's that were on it, 
then span multiple physical devices (I'm assuming that the physical 
devices are not RAID devices and that you haven't carefully allocated 
your LV's so that they only stay on one PV).

When I use LVM, I tend not to use up all of the physical storage.  I 
create LV's that are sufficient for my needs.  Then over time, I can 
grow them as necessary with the unallocated physical extents.

Hugh