I understand that this near linear performance is one of the differentiators of
Spectrum Scale.
Others with more field experience than me might want to comment on how Lustre
and other distributed filesystem perform as they approaches near full capacity.
Daniel
Dr Daniel Kidger
IBM Technical Sales Specialist
Software Defined Solution Sales
+ 44-(0)7818 522 266
[email protected]
> On 7 Nov 2017, at 00:12, Carl <[email protected]> wrote:
>
> Thanks to all for the information.
>
> Im happy to say that it is close to what I hoped would be the case.
>
> Interesting to see the effect of the -n value. Reinforces the need to think
> about it and not go with the defaults.
>
> Thanks again,
>
> Carl.
>
>
>> On 7 November 2017 at 03:18, Achim Rehor <[email protected]> wrote:
>> I have no practical experience on these numbers, however, Peters experience
>> below is matching what i learned from Dan years ago.
>>
>> As long as the -n setting of the FS (the number of nodes potentially
>> mounting the fs) is more or less matching the actual number of mounts,
>> this 99.x % before degradation is expected. If you are far off with that -n
>> estimate, like having it set to 32, but the actual number of mounts is in
>> the thousands,
>> then degradation happens earlier, since the distribution of free blocks in
>> the allocation maps is not matching the actual setup as good as it could be.
>>
>> Naturally, this depends also on how you do filling of the FS. If it is only
>> a small percentage of the nodes, doing the creates, then the distribution
>> can
>> be 'wrong' as well, and single nodes run earlier out of allocation map
>> space, and need to look for free blocks elsewhere, costing RPC cycles and
>> thus performance.
>>
>> Putting this in numbers seems quite difficult ;)
>>
>>
>> Mit freundlichen Grüßen / Kind regards
>> Achim Rehor
>>
>>
>> Software Technical Support Specialist AIX/ Emea HPC Support
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>>
>> From: Peter Smith <[email protected]>
>> To: gpfsug main discussion list <[email protected]>
>> Date: 11/06/2017 09:17 AM
>> Subject: Re: [gpfsug-discuss] Performance of GPFS when filesystem is
>> almost full
>> Sent by: [email protected]
>>
>>
>>
>>
>> Hi Carl.
>>
>> When we commissioned our system we ran an NFS stress tool, and filled the
>> system to the top.
>>
>> No performance degradation was seen until it was 99.7% full.
>>
>> I believe that after this point it takes longer to find free blocks to write
>> to.
>>
>> YMMV.
>>
>> On 6 November 2017 at 03:35, Carl <[email protected]> wrote:
>> Hi Folk,
>>
>> Does anyone have much experience with the performance of GPFS as it becomes
>> close to full. In particular I am referring to split data/meta data, where
>> the data pool goes over 80% utilisation.
>>
>> How much degradation do you see above 80% usage, 90% usage?
>>
>> Cheers,
>>
>> Carl.
>>
>>
>>
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>>
>>
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