Hi all,
according to several GPFS presentations as well as according to the man pages:
Table 1. Block sizes and subblock sizes
+-------------------------------+-------------------------------+
| Block size | Subblock size |
+-------------------------------+-------------------------------+
| 64 KiB | 2 KiB |
+-------------------------------+-------------------------------+
| 128 KiB | 4 KiB |
+-------------------------------+-------------------------------+
| 256 KiB, 512 KiB, 1 MiB, 2 | 8 KiB |
| MiB, 4 MiB | |
+-------------------------------+-------------------------------+
| 8 MiB, 16 MiB | 16 KiB |
+-------------------------------+-------------------------------+
A block size of 8MiB or 16MiB should contain subblocks of 16KiB.
However, when creating a new filesystem with 16MiB blocksize, looks like is
using 128KiB subblocks:
[root@merlindssio01 ~]# mmlsfs merlin
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
.
.
.
-n 128 Estimated number of nodes that
will mount file system
-B 1048576 Block size (system pool)
16777216 Block size (other pools)
.
.
.
What am I missing? According to documentation, I expect this to be a fixed
value, or it isn't at all?
On the other hand, I don't really understand the concept 'Indirect block size
in bytes', can somebody clarify or provide some details about this setting?
Thanks a lot and best regards,
Marc
_________________________________________
Paul Scherrer Institut
High Performance Computing
Marc Caubet Serrabou
Building/Room: WHGA/019A
Forschungsstrasse, 111
5232 Villigen PSI
Switzerland
Telephone: +41 56 310 46 67
E-Mail: marc.cau...@psi.ch
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