[linux-lvm] Re: Software raid on top of lvm logical volume
Michael T. Babcock
mike at mikebabcock.ca
Tue Nov 2 15:46:57 UTC 2004
Erik Ohrnberger wrote:
>This solution would seem to be as the holy grail in that it would give you
>the best of all worlds: resizable RAID storage. Or am I wrong about this
>assumption?
>
>
I've been trying to figure out a reason why it wouldn't be doable for a
few weeks now.
Currently, one can create RAID-0 like performance with LVM2 by
specifying stripes for one's LVs. Why not:
lvcreate -L 3GB --raid-level 5 --stripes 3 -n SafeData VG001 /dev/sda
/dev/sdb /dev/sdc
PV section 1 on sda and sdb are data, section 1 on sdc is XOR data. PV
section 2 on sda and sdc are data, and XOR data on section 2 of sdb, and
so on.
One of the major performance implications would be the larger block
sizes being dealt with; many people seem to find smaller stripes better
for performance in RAID-0/5 situations, and by default one would have
4MB stripes. With some effort, I'm sure this could be rectified as well.
Thoughts? Or should I blog about it instead? ;-)
If I didn't have multiple out-of-town server and firewall installations
this week, I'd code instead :-)
--
Michael T. Babcock
http://mikebabcock.ca
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