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Re: [linux-lvm] Re: Software raid on top of lvm logical volume



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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