[mythtv-users] RAID 5 of different sized disks for mythtv storage?

Tony Lill ajlill at ajlc.waterloo.on.ca
Mon Sep 11 22:45:09 UTC 2006

RAID5 is an excellent idea. Never, ever, spread a logical volume
across multiple disks unless you have raid behind them. You're just
asking for pain.

A RAID5 requires the same size partitions on 3 or more disks. So if you
stick with the 50G partitions, you can make some raid5 partitions
using all 4 of your disks, and some more if you have space left on 3,
and then mirror the remaining space. That will maximize your space
while giving you redundancy.

Maybe this ascii art will help. hda is your 250 with the other stuff,
hdb is your 200 and hdc and hdd are your 300's. md0 and md4 are raid5
with 3 disks, md1..md3 are raid5 with 4 disks, and md5, md6 are raid1

hda   hdb    hdc hdd
OS    md0-----------
md4          md4----

Tony Lill,                         Tony.Lill at AJLC.Waterloo.ON.CA
President, A. J. Lill Consultants        fax/data (519) 650 3571
539 Grand Valley Dr., Cambridge, Ont. N3H 2S2     (519) 241 2461
--------------- http://www.ajlc.waterloo.on.ca/ ----------------
"Welcome to All Things UNIX, where if it's not UNIX, it's CRAP!"

"Paul V. Gratz" <pgratz at gratz1.com> writes:

> Hey all,
>   I'm fairly early in the contemplation stage of setting up RAID for
> my backend storage needs.  Currently I've got LVM setup across three
> drives: part of a 250GB drive, all of a 200GB drive and all of a 300GB
> drive.  Those drives are broken up into 50GB partitions to make it
> easier to shift things around w/ LVM when the time comes.  I just
> bought a new 300GB drive.  
>   Setting aside the issue of each drive needing to be on its own IDE
> bus (right now they share but I'm planning on picking up a new
> controller card to get to one drive per bus).  Is there a way to use
> RAID5 on 50GB partitions spread across several disks or is that asking
> for trouble.  I think I remember someone mentioning having that kind
> of setup.  Alternatively it sounds like I either need to get one more
> 300GB drive or settle on 250GBs for the RAID setup wasting the last
> 50GB of the two 300GB drives to make this work.  Is this correct?
>   I've read the two wiki pages on the subject but they don't really
> answer my question (although it looks like they have great info on how
> to set it up once I figure out the partitioning stuff).
> Thanks!
> Paul
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