[Linux-PowerEdge] Linux-PowerEdge Digest, Vol 102, Issue 6

Gregory Gulik ggulik at reachmail.com
Mon Nov 5 11:02:55 CST 2012


Thanks, that's a good suggestion, but in this particular case I want 
maximum size and maximum performance is not required.  I do have the 
rest of the slots in the MD1000 with 15k RPM SAS drives with a separate 
filesystem that will be for our performance critical systems.

I'm merely trying to make sure that given the slow(er) drives in a 
RAID-6 configuration I would like to ensure the performance is as good 
as it should be given those trade-offs.


On 11/5/12 10:57 AM, John Lloyd wrote:
>
>
> You have a couple of trade-offs here.  There was a bunch of (very good) advice about aligning stripe units and stripe widths.
>
> Or you could buy 4 more 2TB SATA disks, run RAID-10, keep your 12TB total, and avoid the whole striping logic analysis thing and issues with performance.  RAID-10 is faster for more kinds of IO patterns than RAID-5 or RAID-6.    And when a drive breaks, the volume rebuild time is only a couple of hours not a couple of days.
>
> The trade-offs of course are money vs performance vs effort to get the system running.
>
> One other hint:  set the the IO readahead size.  The command blockdev --setra is another good thing to do for read IO.
>
>
> --John
>
>
>
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-- 
Gregory Gulik

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