Not to be too pedantic, but I believe the the subblock size is 1/32 of the
block size (which strengthens Luis’s arguments below).
I thought the the original question was NOT about inode size, but about
metadata block size. You can specify that the system pool have a different
block size from the rest of the filesystem, providing that it ONLY holds
metadata (—metadata-block-size option to mmcrfs).
So with 4K inodes (which should be used for all new filesystems without some
counter-indication), I would think that we’d want to use a metadata block size
of 4K*32=128K. This is independent of the regular block size, which you can
calculate based on the workload if you’re lucky.
There could be a great reason NOT to use 128K metadata block size, but I don’t
know what it is. I’d be happy to be corrected about this if it’s out of whack.
--
Stephen
> On Sep 22, 2016, at 3:37 PM, Luis Bolinches <luis.bolinc...@fi.ibm.com> wrote:
>
> Hi
>
> My 2 cents.
>
> Leave at least 4K inodes, then you get massive improvement on small files
> (less 3.5K minus whatever you use on xattr)
>
> About blocksize for data, unless you have actual data that suggest that you
> will actually benefit from smaller than 1MB block, leave there. GPFS uses
> sublocks where 1/16th of the BS can be allocated to different files, so the
> "waste" is much less than you think on 1MB and you get the throughput and
> less structures of much more data blocks.
>
> No warranty at all but I try to do this when the BS talk comes in: (might
> need some clean up it could not be last note but you get the idea)
>
> POSIX
> find . -type f -name '*' -exec ls -l {} \; > find_ls_files.out
> GPFS
> cd /usr/lpp/mmfs/samples/ilm
> gcc mmfindUtil_processOutputFile.c -o mmfindUtil_processOutputFile
> ./mmfind /gpfs/shared -ls -type f > find_ls_files.out
> CONVERT to CSV
>
> POSIX
> cat find_ls_files.out | awk '{print $5","}' > find_ls_files.out.csv
> GPFS
> cat find_ls_files.out | awk '{print $7","}' > find_ls_files.out.csv
> LOAD in octave
>
> FILESIZE = int32 (dlmread ("find_ls_files.out.csv", ","));
> Clean the second column (OPTIONAL as the next clean up will do the same)
>
> FILESIZE(:,[2]) = [];
> If we are on 4K aligment we need to clean the files that go to inodes
> (WELL not exactly ... extended attributes! so maybe use a lower number!)
>
> FILESIZE(FILESIZE<=3584) =[];
> If we are not we need to clean the 0 size files
>
> FILESIZE(FILESIZE==0) =[];
> Median
>
> FILESIZEMEDIAN = int32 (median (FILESIZE))
> Mean
>
> FILESIZEMEAN = int32 (mean (FILESIZE))
> Variance
>
> int32 (var (FILESIZE))
> iqr interquartile range, i.e., the difference between the upper and lower
> quartile, of the input data.
>
> int32 (iqr (FILESIZE))
> Standard deviation
>
>
> For some FS with lots of files you might need a rather powerful machine to
> run the calculations on octave, I never hit anything could not manage on a
> 64GB RAM Power box. Most of the times it is enough with my laptop.
>
>
>
> --
> Ystävällisin terveisin / Kind regards / Saludos cordiales / Salutations
>
> Luis Bolinches
> Lab Services
> http://www-03.ibm.com/systems/services/labservices/
>
> IBM Laajalahdentie 23 (main Entrance) Helsinki, 00330 Finland
> Phone: +358 503112585
>
> "If you continually give you will continually have." Anonymous
>
>
> ----- Original message -----
> From: Stef Coene <stef.co...@docum.org>
> Sent by: gpfsug-discuss-boun...@spectrumscale.org
> To: gpfsug main discussion list <gpfsug-discuss@spectrumscale.org>
> Cc:
> Subject: Re: [gpfsug-discuss] Blocksize
> Date: Thu, Sep 22, 2016 10:30 PM
>
> On 09/22/2016 09:07 PM, J. Eric Wonderley wrote:
> > It defaults to 4k:
> > mmlsfs testbs8M -i
> > flag value description
> > ------------------- ------------------------
> > -----------------------------------
> > -i 4096 Inode size in bytes
> >
> > I think you can make as small as 512b. Gpfs will store very small
> > files in the inode.
> >
> > Typically you want your average file size to be your blocksize and your
> > filesystem has one blocksize and one inodesize.
>
> The files are not small, but around 20 MB on average.
> So I calculated with IBM that a 1 MB or 2 MB block size is best.
>
> But I'm not sure if it's better to use a smaller block size for the
> metadata.
>
> The file system is not that large (400 TB) and will hold backup data
> from CommVault.
>
>
> Stef
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