[gpfsug-discuss] Metadata usage almost doubled after policy run with migration rule

Billich Heinrich Rainer (ID SD) heinrich.billich at id.ethz.ch
Tue Jun 8 10:04:19 BST 2021




A policy run with ‘-I defer’ and a placement rule did almost double the metadata usage of a filesystem. This filled the metadata disks to a critical level. I would like to understand if this is to be expected and ‘as designed’ or if I face some issue or bug. 

 I hope a subsequent run of ‘mmrstripefs -p’ will reduce the metadata usage again.

Thank you



I want to move all data to a new storage pool and did run a policy like


RULE 'migrate_to_Data'



  TO POOL 'Data'


 for each fileset with 


  mmapplypolicy -I defer


Next I want to actually move the data with 


  mmrestripefs -p


After the policy run metadata usage increased from 2.06TiB to 3.53TiB and filled the available metadata space by >90%. This is somewhat surprising. Will the following  run of ‘mmrestripefs -p’ reduce the usage again, when the files are not illplaced any more? The number of used Inodes did not change noticeably during the policy run. 


Or maybe illplaced files use larger inodes? Looks like for each used inode we increased by about 4k: 400M inodes, 1.6T increase in size


Thank you,




Some details


# mmlsfs  fsxxxx -f -i -B -I -m -M -r -R -V

flag                value                    description

------------------- ------------------------ -----------------------------------

 -f                 8192                     Minimum fragment (subblock) size in bytes (system pool)

                    32768                    Minimum fragment (subblock) size in bytes (other pools)

 -i                 4096                     Inode size in bytes

 -B                 1048576                  Block size (system pool)

                    4194304                  Block size (other pools)

 -I                 32768                    Indirect block size in bytes

 -m                 1                        Default number of metadata replicas

 -M                 2                        Maximum number of metadata replicas

 -r                 1                        Default number of data replicas

 -R                 2                        Maximum number of data replicas

 -V                 23.00 (          Current file system version

                    19.01 (          Original file system version


Inode Information


Total number of used inodes in all Inode spaces:          398502837

Total number of free inodes in all Inode spaces:           94184267

Total number of allocated inodes in all Inode spaces:     492687104

Total of Maximum number of inodes in all Inode spaces:    916122880

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