On Tue, 2006-09-19 at 15:40 -0700, Scott Lamb wrote: > On Sep 18, 2006, at 12:37 PM, Mark Krenz wrote: > > LVM != RAID > > > > You should have been doing RAID if you wanted to be able to > > handle the > > failure of one drive. > > This is my biggest beef with LVM - why doesn't *any* of the > documentation point this out? There are very few good reasons to use > LVM without RAID, and "ignorance" certainly isn't among them. I don't > see any mention of RAID or disk failures in the manual pages or in > the HOWTO. > > For example, the recipes chapter [1] of the HOWTO shows a non-trivial > setup with four volume groups split across seven physical drives. > There's no mention of RAID. This is a ridiculously bad idea - if > *any* of those seven drives are lost, at least one volume group will > fail. In some cases, more than one. This document should be showing > best practices, and it's instead showing how to throw away your data. > > The "lvcreate" manual page is pretty bad, too. It mentions the > ability to tune stripe size, which on casual read, might suggest that > it uses real RAID. Instead, I think this is just RAID-0. > > [1] - http://tldp.org/HOWTO/LVM-HOWTO/recipeadddisk.html > LVM is just a Logical Volume Manager. It sounds like it add a layer between physical devices and logical volumes. A such layer can take care of physical devices failure, but lvm does not. Maybe you are right and it should be pointed out. Maybe not ... Having a half block device make no sense because there are actually no filesystem capable of recovering this kind of failure. -- Fabien Jakimowicz <fabien@jakimowicz.com>
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