[PLUG] striping in LVM or md?

Eric Wilhelm scratchcomputing at gmail.com
Thu Jun 7 03:01:51 UTC 2007


# from Eli Stair
# on Wednesday 06 June 2007 02:00 pm:

>On 6/6/07, Eric Wilhelm <scratchcomputing at gmail.com> wrote:
>> I've got four SATA disks and want to setup a raid 10 with md.
>>
>> I'll be using md to create two mirror pairs.

>In short, I'd suggest using the md-raid10 module.  It handles in one
>module/management point the striping/mirroring.

I forgot to mention that I have a pair of 120GB disks and one pair of 
160GB disks.  Does that change the answer.

On further reading, it sounds like md wants similar-sized devices for 
raid0, though I guess I could do "linear" on top of raid1?

>Feel free to layer LVM on top.

Wouldn't that cost me just as much (or more) performance than doing the 
striping in LVM?  That's mainly what I was wondering with the original 
question.  i.e. if I'm doing LVM anyway, it couldn't possibly be 
without cpu cost, so shouldn't I just mirror in md and then make a VG 
out of md0 and md1?

Anybody got any references to benchmarks on that?  All google gives me 
is questions.

Thanks,
Eric
-- 
"You can't win. You can't break even. You can't quit."
--Ginsberg's Restatement of the Three Laws of Thermodynamics
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