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

[Sobey, Richard A]

So it could be that we didn’t really know what we were doing when our system was installed (and still don’t by some of the messages I post *cough*) but basically I think we’re quite similar to other shops where we resell GPFS to departmental users internally and it just made some sense to break down each one into a fileset. We can then snapshot each one individually (7402 snapshots at the moment) and apply quotas.

I know your question was why independent and not dependent – but I honestly don’t know. I assume it’s to do with not crossing the streams if you’ll excuse the obvious film reference.

Richard

From: gpfsug-discuss-bounces at spectrumscale.org [mailto:gpfsug-discuss-bounces at spectrumscale.org] On Behalf Of Stephen Ulmer
Sent: 18 May 2017 15:48
To: gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Subject: Re: [gpfsug-discuss] What is an independent fileset? was: mmbackup with fileset : scope errors

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]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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