[gpfsug-discuss] Blocksize

[Greg.Lehmann at csiro.au]

Are there any presentation available online that provide diagrams of the directory/file creation process and modifications in terms of how the blocks/inodes and indirect blocks etc are used. I would guess there are a few different cases that would need to be shown.

This is the sort of thing that would great in a decent text book on GPFS (doesn't exist as far as I am aware.)

Cheers,

Greg

From: gpfsug-discuss-bounces at spectrumscale.org [mailto:gpfsug-discuss-bounces at spectrumscale.org] On Behalf Of Marc A Kaplan
Sent: Thursday, 29 September 2016 1:23 AM
To: gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Subject: Re: [gpfsug-discuss] Blocksize

OKAY, I'll say it again.  inodes are PACKED into a single inode file.  So a 4KB inode takes 4KB, REGARDLESS of metadata blocksize.  There is no wasted space.

(Of course if you have metadata replication = 2, then yes, double that.  And yes, there overhead for indirect blocks (indices), allocation maps, etc, etc.)

And your choice is not just 512 or 4096.  Maybe 1KB or 2KB is a good choice for your data distribution, to optimize packing of data and/or directories into inodes...

Hmmm... I don't know why the doc leaves out 2048, perhaps a typo...

mmcrfs x2K -i 2048

[root at n2 charts]# mmlsfs x2K -i
flag                value                    description
------------------- ------------------------ -----------------------------------
 -i                 2048                     Inode size in bytes

Works for me!
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