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migration criteria. This goal may not be attainable if the total size of all files not eligible for migration is
large.
Total Migration Streams. This value determines the degree of parallelism in the file migration process.
This applies to policies using the Migrate Files and Migrate Files and Purge options only (see File and
Volume Options below).
File and Volume Options. There are four options available for determining how tape migration handles
files and volumes. Only one of these options may be selected at a time.
Migrate Volumes. Entire volumes are selected for migration. All segments on a selected volume
will be migrated either downward in the hierarchy or laterally within the same storage level,
leaving the volume ready for reclaiming.
MPS selects tape virtual volumes in EOM state with the greatest amount of vacated space. The
storage segments on the selected volumes are either moved to another volume in the same storage
class or are migrated downwards in the hierarchy based on the Migration Policy settings and the
last read and write times for each file. When the migration step is complete, the migrated
volumes' Condition should be EMPTY and the volumes should be ready to be reclaimed.
This algorithm is useful for managing space in tape storage classes without having to run repack
manually. Manually reclaiming of empty volumes may still be necessary. Note that this migration
algorithm moves storage segments laterally or downwards, but is not able to make multiple
copies. Also, note that segments selected for migration are selected based on the volume in
which they reside, not any other criteria.
A storage class configured with a migration policy using Migrate Volumes will
not be considered as a valid alternate copy from which to retry a failed read or
stage operation. No storage class to which such a storage class migrates,
directly or indirectly, will be considered as a valid retry candidate, either. See
the description of the Auto Stage Retry and Auto Read Retry flags in section
6.3.2, Class of Service Configuration Window on page 175.
Migrate Volumes and Whole Files. Similar to the Migrate Volumes option with the addition
that all segments belonging to any file with a segment on the source volume will be migrated. For
example, if a file consists of segments on two volumes, and one volume is selected for migration,
then the segments of the file on the other volume will be migrated as well.
This algorithm tends to keep all of the segments in a file at the same level in the hierarchy and on
the same volumes. Note that using this algorithm can result in large numbers of tape volumes
being active at once, and hence large numbers of tape mounts.
A storage class configured with a migration policy using Migrate Volumes and
Whole Files will not be considered as a valid alternate copy from which to retry
a failed read or stage operation. No storage class to which such a storage class
migrates, directly or indirectly, will be considered as a valid retry candidate,
either. See the description of the Auto Stage Retry and Auto Read Retry flags
in section 6.3.2, Class of Service Configuration Window on page 175.
Migrate Files. A duplicate copy of the tape files will be made at the next lower level in the
hierarchy.
This enables a tape migration algorithm which is similar to disk migration. This algorithm is
HPSS Management Guide November 2009
Release 7.3 (Revision 1.0) 187