[gpfsug-discuss] Blocksize

Marc A Kaplan makaplan at us.ibm.com
Wed Sep 28 16:23:12 BST 2016


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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