[gpfsug-discuss] du --apparent-size and quota

[IBM Spectrum Scale]

Hi,
The data and metadata replications are 2 on both source and destination
filesystems, so from:

$ mmrepquota -j srcfilesys | grep fileset
srcfileset FILESET         800        800        800          0     none |
863       0        0
        0     none

$ mmrepquota -j dstfilesys | grep fileset
fileset root       FILESET         457        400        400          0
none |      853       0
       0        0     none

the quota data should be changed from 800G to 457G (or 400G to 228.5G),
after "rsync -AHS".


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From:	Ulrich Sibiller <u.sibiller at science-computing.de>
To:	Kumaran Rajaram <krajaram at geocomputing.net>, gpfsug main
            discussion list <gpfsug-discuss at spectrumscale.org>,
            "gpfsug-discuss at gpfsug.org" <gpfsug-discuss at gpfsug.org>
Date:	06/02/2021 06:16 PM
Subject:	[EXTERNAL] Re: [gpfsug-discuss] du --apparent-size and quota
Sent by:	gpfsug-discuss-bounces at spectrumscale.org



On 6/1/21 6:08 PM, Kumaran Rajaram wrote:
>>> If I'm not mistaken even with SS5 created filesystems, 1 MiB FS block
size implies 32 kiB sub blocks (32 sub-blocks).
>
> Just to add: The /srcfilesys seemed to have been created with GPFS
version 4.x which supports only 32 sub-blocks per block.
>
> -T                 /srcfilesys              Default mount point
> -V                 16.00 (4.2.2.0)          Current file system version
>                     14.10 (4.1.0.4)          Original file system version
> --create-time      Tue Feb  3 11:46:10 2015 File system creation time
> -B                 1048576                  Block size
> -f                 32768                    Minimum fragment (subblock)
size in bytes
> --subblocks-per-full-block 32               Number of subblocks per full
block
>
>
> The /dstfilesys was created with GPFS version 5.x which support greater
than 32 subblocks per block. /dstfilesys does have 512
subblocks-per-full-block with 8KiB subblock size since file-system
blocksize is 4MiB.
>
>
> -T                 /dstfilesys              Default mount point
> -V                 23.00 (5.0.5.0)          File system version
> --create-time      Tue May 11 16:51:27 2021 File system creation time
> -B                 4194304                  Block size
> -f                 8192                     Minimum fragment (subblock)
size in bytes
> --subblocks-per-full-block 512              Number of subblocks per full
block
>

Well, from the higher flexibility in terms of the number of subblocks I'd
expect a lower disk usage
instead of a higher one. Is this a wrong assumption? From 400G to 457G it's
a ~13% increase!

> Beside the overhead, hard-links in the source FS (which, if I'm not
mistaken, are not handled by "rsync" unless you specify "-H") and in some
cases spare files can also explain the differences.

My rsync is using -AHS, so this should not be relevant here.

Uli

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