[Lustre-discuss] Clarification on DDN performance best practices

[Kit Westneat]

> I've seen conflicting statements regarding this. Are you saying that 2 
> tiers should be the max? Or is it advantageous to create OSTs that span 
> many more? I've seen indication of up to 12 tiers to maximize write 
> performance. Any insight would help.
>
>   
If I recall correctly, the test was performed with 1 tier per LUN vs two 
tiers per LUN, and two tiers had better performance. However, with the 
larger drives, especially in the SATA world, you quickly start to hit 
the 8TB ext3 limit. With the 1TB drives, you hit that limit in one tier, 
so obviously this advice is not applicable to these large disks.
> Also, when creating LUNs on a DDN to be use exclusively for OSTs, does 
> in make sense to use a disk block size of 4K (instead of 512bytes) since 
> the standard block size for luster is also 4K.
>   
4k blocks are also a good idea because the S2As prefer that IO be 
aligned on 4k boundries.

- Kit
> Thanks,
> /pgc
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>   


-- 
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Kit Westneat
kwestneat at datadirectnet.com
812-484-8485