[gpfsug-discuss] subblock sanity check in 5.0

[Joseph Mendoza]

Hi, it's for a traditional NSD setup.

--Joey


On 6/26/18 12:21 AM, Sven Oehme wrote:
> Joseph,
>
> the subblocksize will be derived from the smallest blocksize in the filesytem, given you specified a metadata block
> size of 512k thats what will be used to calculate the number of subblocks, even your data pool is 4mb. 
> is this setup for a traditional NSD Setup or for GNR as the recommendations would be different. 
>
> sven
>
> On Tue, Jun 26, 2018 at 2:59 AM Joseph Mendoza <jam at ucar.edu <mailto:jam at ucar.edu>> wrote:
>
>     Quick question, anyone know why GPFS wouldn't respect the default for
>     the subblocks-per-full-block parameter when creating a new filesystem? 
>     I'd expect it to be set to 512 for an 8MB block size but my guess is
>     that also specifying a metadata-block-size is interfering with it (by
>     being too small).  This was a parameter recommended by the vendor for a
>     4.2 installation with metadata on dedicated SSDs in the system pool, any
>     best practices for 5.0?  I'm guessing I'd have to bump it up to at least
>     4MB to get 512 subblocks for both pools.
>
>     fs1 created with:
>     # mmcrfs fs1 -F fs1_ALL -A no -B 8M -i 4096 -m 2 -M 2 -r 1 -R 2 -j
>     cluster -n 9000 --metadata-block-size 512K --perfileset-quota
>     --filesetdf -S relatime -Q yes --inode-limit 20000000:10000000 -T /gpfs/fs1
>
>     # mmlsfs fs1
>     <snipped>
>
>     flag                value                    description
>     ------------------- ------------------------
>     -----------------------------------
>      -f                 8192                     Minimum fragment (subblock)
>     size in bytes (system pool)
>                         131072                   Minimum fragment (subblock)
>     size in bytes (other pools)
>      -i                 4096                     Inode size in bytes
>      -I                 32768                    Indirect block size in bytes
>
>      -B                 524288                   Block size (system pool)
>                         8388608                  Block size (other pools)
>
>      -V                 19.01 (5.0.1.0)          File system version
>
>      --subblocks-per-full-block 64               Number of subblocks per
>     full block
>      -P                 system;DATA              Disk storage pools in file
>     system
>
>
>     Thanks!
>     --Joey Mendoza
>     NCAR
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