[gpfsug-discuss] Combined system (metadata) and data pool on GPFS 5.x?

[Simon Thompson]

I wasn't but ...

If your metadata is in the same RG/DA as your data, even if it’s a separate pool, the contention is the same. But if you have 2 DAs, then you have more spinning disks underneath to provide iops anyway.

We only separate our metadata and data into pools because we want to replicate the metadata between DSS-G systems, but not data. And also have some data which is replicated but not all, and the only way we could figure to do that is by having separate pools and failure groups. i.e. we didn't want data in the system pool that wasn't replicated being placed on the second site.

And I agree, block sizes don't matter so much anymore, except remember the "variable" sub-blocks are based on the smallest block size used, so we ended up with 16MB blocks for both data and metadata.

Simon

On 04/07/2019, 04:56, "gpfsug-discuss-bounces at spectrumscale.org on behalf of Ryan Novosielski" <gpfsug-discuss-bounces at spectrumscale.org on behalf of novosirj at rutgers.edu> wrote:

    Hi there,
    
    Was at the Lenovo GNR/GPFS 5.x seminar the other week and we briefly discussed whether or not the recommendation was to place data in the system pool (eg. have one combined system/data pool), or to have them separate. We’ve got a GSS26 that we are creating new filesystems on for high speed scratch (16 MB blocks).
    
    I unfortunately did not note all of the considerations/caveats related to this choice. Does anyone who knows/was there and can remember remind me?
    
    The recollection I have is that you may have some contention for I/O if your metadata is on your data disks, and you won’t be able to have different redundancy settings. Once upon a time, block size also mattered, but not so much on 5.x.
    
    Thanks!
    
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