Lustre discuss - Dec 2009 - What stripe size and extent size to choose for Lustre

Hi Guys,

I am new to Lustre and will be deploying a small 20 node cluster using the
Lustre FS.  I do not have many requirements from my users :( and not sure
what type of workload they will be putting on this filesystem.  All nodes
will be interconnected using Infiniband.  My question is what stripe size
and extent size to use for my environment:

Stripe Size: I was thinking of just setting this to -1 since I will be
adding more OSS''s at a later time and will probably have 4-5
OST''s per OSS.
Any downfalls of using -1?
Extent Size: I was thinking of setting this to 1MB.

Regards,
-Simran
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On 2009-12-29, at 20:05, Jagga Soorma wrote:
> I am new to Lustre and will be deploying a small 20 node cluster  
> using the Lustre FS.  I do not have many requirements from my users : 
> ( and not sure what type of workload they will be putting on this  
> filesystem.  All nodes will be interconnected using Infiniband.  My  
> question is what stripe size and extent size to use for my  
> environment:
>
> Stripe Size: I was thinking of just setting this to -1 since I will  
> be adding more OSS''s at a later time and will probably have 4-5  
> OST''s per OSS.  Any downfalls of using -1?
Do you mean "stripe count"?  Having a default stripe count of 4
isn''t
a bad idea, but making the default larger than this is probably not  
going to help.  Adding more stripes is useful if you have many clients  
accessing the same large file, or if a single client needs more  
bandwidth than what a single OST can provide.  Otherwise, adding more  
stripes just adds overhead to file IO.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.