Oracle HSM - Filesystem Metadata Usage Is Very High When Using ssum
Last updated on OCTOBER 31, 2016
Applies to:Oracle Hierarchical Storage Manager (HSM) and StorageTek QFS Software - Version 6.1 and later
Information in this document applies to any platform.
When using 'ssum' for all (or a significant amount) of files on a filesystem, the customer may notice that their meta data space is consumed more than typical and some file system utilities may take longer to run
Changes in 6.1 for the storing of the 'message-digest' (checksum) have been put in the meta data section. For each file that has an extended attribute defined which is used to store the checksum, a 'hidden' directory namespace is created. Within this namespace, a message-digest file is created to store the checksum. This adds additional inode allocations to the 'regular' file (one for the directory and one for the file) in the meta data portion of the file system.
For more information on extended attributes see the 'man runat' and also 'man -s5 fsattr' commands. The extended attributes are a Solaris construct and O-HSM uses this to associate a message-digest file to the 'regular' file.
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