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Tivoli Space Manager for UNIX Using the Hierarchical Storage Management Clients

Build a New Migration Candidates List

A migration candidates list is a prioritized list of files in your file system that are eligible for automatic migration at the time the list is built. The HSM client uses the list to determine which files to migrate and the order in which to migrate them during threshold and demand migration. Immediately prior to migration, each file is checked again to determine whether it is still eligible for migration.

The dsmscoutd daemon continuously scans your managed filesystems for candidate requests from the automatic migration processes, and for elapsed scan-interval hours of all your HSM-managed file systems. A slave scout daemon is started to scan for new candidates. After a candidate scan is completed for your file system, a new migration candidates list is created and the slave scout daemon ends. Another slave scout daemon for the same file system is started after the number of hours you specified on the candidatesinterval option in your dsm.sys file.

The maximum number of slave scout daemons that can scan in parallel on your system is five. You can change this number on the maxcandprocs option in your dsm.sys file. When the dsmscoutd daemon locates the maximum number of eligible candidates, it stops scanning your file system and stores the list. Use the candidatesinterval option in your dsm.sys file to specify how many hours must elapse before the dsmscoutd daemon runs again. Use the minmigfilesize option in your dsm.sys file to specify the minimum file size, in bytes, for a file to be eligible as a candidate for automigration. The dsmscoutd daemon improves the quality of an existing candidates list during each run.

The dsmscoutd daemon manages two candidates pools (APool and BPool) for each filesystem. These pools are located in /etc/adsm/SpaceMan/candidatesPools. The dsmautomig process uses the APool, while the dsmscoutd daemon periodically refreshes the BPool. Each pool has a maximum size of 10000 KB each. If the dsmautomig process migrates all candidates from the APool, the BPool then converts to the APool and the dsmscoutd daemon immediately starts to build a new BPool. Specify the maximum number of migration candidates that the dsmscoutd daemon should search for with the maxcandidates option on the dsmmigfs command. Candidates that require more space are not included. The dsmscoutd daemon stores fewer candidates if there is insufficient storage in the parent filesystem of /etc/adsm/SpaceMan/candidatesPools.

Attention: If your system root filesystem does not have sufficient capacity to store this information, either increase capacity, or create a dedicated filesystem with sufficient size mounted to /etc/adsm/SpaceMan/candidatesPools. Kill all running dsmscoutd processes. Create and mount the dedicated file system. Restart the scout daemon manually, using the dsmscoutd command.

For a file to be eligible for automatic migration, it must:

The HSM client prioritizes files for migration based on the number of days since they were last accessed, their size, and the age and size factors that you set for your file systems. The age factor determines how much consideration is given to the number of days since a file was last accessed, and the size factor determines how much consideration is given to the size of a file.


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