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Re: [linux-lvm] Misleading documentation (was: HDD Failure)



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

--
Scott Lamb <http://www.slamb.org/>



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