[gpfsug-discuss] What is an independent fileset? was: mmbackup with fileset : scope errors

[Stephen Ulmer]

Each independent fileset is an allocation area, and they are (I believe) handled separately. There are a set of allocation managers for each file system, and when you need to create a file you ask one of them to do it. Each one has a pre-negotiated range of inodes to hand out, so there isn’t a single point of contention for creating files. I’m pretty sure that means that they all have to have a range for each inode space. This is based on my own logic, and could be complete nonsense.

While I’m sure that limit could be changed eventually, there’s probably some efficiencies in not making it much bigger than it needs to be. I don’t know if it would take an on-disk format change or not.


So how do you decide that a use case gets it’s own fileset, and do you just always use independent or is there an evaluation? I’m just curious because I like to understand lots of different points of view — feel free to tell me to go away. :)

-- 
Stephen



> On May 18, 2017, at 10:32 AM, Sobey, Richard A <r.sobey at imperial.ac.uk <mailto:r.sobey at imperial.ac.uk>> wrote:
> 
> Thanks, I was just about to post that, and I guess is still the reason a dependent fileset is still the default without the –inode-space new option fileset creation.
>  
> I do wonder why there is a limit of 1000, whether it’s just IBM not envisaging any customer needing more than that? We’ve only got 414 at the moment but that will grow to over 500 this year. 
>  
> Richard
>  
> From: gpfsug-discuss-bounces at spectrumscale.org <mailto:gpfsug-discuss-bounces at spectrumscale.org> [mailto:gpfsug-discuss-bounces at spectrumscale.org <mailto:gpfsug-discuss-bounces at spectrumscale.org>]On Behalf Of David D. Johnson
> Sent: 18 May 2017 15:24
> To: gpfsug main discussion list <gpfsug-discuss at spectrumscale.org <mailto:gpfsug-discuss at spectrumscale.org>>
> Subject: Re: [gpfsug-discuss] What is an independent fileset? was: mmbackup with fileset : scope errors
>  
> Here is one big reason independent filesets are problematic:
> A5.13:
> Table 43. Maximum number of filesets
> Version of GPFS
> Maximum Number of Dependent Filesets
> Maximum Number of Independent Filesets
> IBM Spectrum Scale V4
> 10,000
> 1,000
> GPFS V3.5
> 10,000
> 1,000
> Another is that each independent fileset must be sized (and resized) for the number of inodes it is expected to contain.
> If that runs out (due to growth or a runaway user job), new files cannot be created until the inode limit is bumped up.
> This is true of the root namespace as well, but there’s only one number to watch per filesystem. 
>  
>  — ddj
> Dave Johnson
> Brown University
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