[Lustre-discuss] mkfs options/tuning for RAID based OSTs

Edward Walter ewalter at cs.cmu.edu
Wed Oct 20 09:30:03 PDT 2010


Hi Denis,

Changing the number of parity disks (RAID5 = 1, RAID6 = 2) doesn't 
change the math on the data disks and data segment size. You still need 
a power of 2 number of data disks to insure that the product of the RAID 
chunk size and the number of data disks is 1MB.

Aside from that; I wouldn't comfortably rely on RAID5 to protect my data 
at this point. We've seen to many dual-disk failures to trust it.

Thanks.

-Ed

Charland, Denis wrote:
> Brian J. Murrell wrote:
>   
>> On Tue, 2010-10-19 at 21:00 -0400, Edward Walter wrote: 
>>   
>>
>> This is why the recommendations in this thread have continued to be
>> using a number of data disks that divides evenly into 1MB (i.e. powers
>> of 2: 2, 4, 8, etc.).  So for RAID6: 4+2 or 8+2, etc.
>>
>>     
>  
> What about RAID5?
>
> Denis
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