[Lustre-discuss] Bad distribution of files among OSTs

Kevin Van Maren Kevin.Vanmaren at Sun.COM
Tue Nov 3 01:05:53 PST 2009


Andreas Dilger wrote:
> On 2009-11-01, at 02:03, Thomas Roth wrote:
>   
>> Could this situation, 10 full OSTs out of 200,
>> lead to a significant drop in performance?
>> Before, we could usually get the full 110MB/s
>> or so over the 1Gbit/s ethernet lines of the clients.
>> That had dropped to about 50%, but we did not
>> find any other odd thing than the filling levels of
>> the OSTs.
>>     
>
> Yes, this is entirely possible.  If the OST is very
> full, then it takes longer to find free blocks.
>   

Longer to find them, and less likely to allocate large contiguous free 
blocks,
so the disk IOs are smaller with more seeks.

Kevin




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