[Lustre-discuss] Limit of OSTs per OSS?

[Arne Wiebalck]

OK, I will keep that in mind.

Thanks,
  Arne

Sébastien Buisson wrote:
> Hi,
> 
> Just a small feedback from our own experience.
> I agree with Brian about the fact that there is no strong limit on the 
> number of OSTs per OSS in the Lustre code. But one should really take 
> into account the available memory on OSSes when defining the number of 
> OSTs per OSS (and so the size of each OST). If you do not have 1GB or 
> 1.2 GB of memory per OST on your OSSes, you will run into serious 
> trouble with "out of memory" messages.
> 
> For instance, if you want 8 OSTs per OSS, your OSSes should have at 
> least 10GB of RAM.
> 
> Unfortunately we experienced those "out of memory" problems, so I advise 
> you to read Lustre Operations Manual chapter 33.12 "OSS RAM Size for a 
> Single OST".
> 
> Cheers,
> Sebastien.
> 
> 
> Arne Wiebalck a écrit :
>> Brian J. Murrell wrote:
>>> On Wed, 2009-08-19 at 11:45 +0200, Arne Wiebalck wrote:
>>>> is there a limit on the number of OSTs per OSS?
>>> I have never run across one so there is likely no *practical* limit.  I
>>> could very well be corrected on this though.
>>>
>>> Unless you are making lots and lots of small OSTs -- which is not
>>> usually beneficial anyway -- typically, you will run into resource
>>> limitations (memory, bus bandwidth, etc.) on an OSS before you hit a
>>> limit on the number of OSTs.
>> I just thought I remembered there was something like 8 OSTs per OSS,
>> but apparently I was wrong.
>>
>>> Just how many OSTs are you considering, and how big will they be?
>> My OSSs will have 10 OSTs with 1TB each.
>>
>> Thanks for the quick reply,
>>  Arne
>>
>>
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