IBM HPSS manual Tape Volume Migration

The purpose of tape file migration is to make an additional copy (or multiple additional copies) of a file, in a tape storage class, to a lower level in the hierarchy. It is also possible to move files downwards instead of copying them. In this case there is no duplicate copy maintained. There is no separate purge component to tape file migration. Empty volumes must be reclaimed using the reclaim utility.

Tape Volume Migration:

The purpose of tape volume migration is to free tape volumes for reuse. Tape volumes are selected based on being in the EOM map state and containing the most unused space (caused by users overwriting or deleting files). The remaining segments on these volumes are either migrated downwards to the next level in the hierarchy, or are moved laterally to another tape volume at the same level. This results in empty tape volumes which may then be reclaimed. Note that there is no purge component to tape volume migration. All of the operations use a move instead of a copy semantic.

•Gatekeeper (GK). The Gatekeeper provides two main services:

·It provides sites with the ability to schedule the use of HPSS resources using the Gatekeeping Service.

·It provides sites with the ability to validate user accounts using the Account Validation Service.

Both of these services allow sites to implement their own policy.

The default Gatekeeping Service policy is to not do any gatekeeping. Sites may choose to implement a policy for monitoring authorized callers, creates, opens, and stages. The Core Server will call the appropriate GK API depending on the requests that the site-implemented policy is monitoring.

The Account Validation Service performs authorizations of user storage charges. A site may perform no authorization, default authorization, or site-customized authorization depending on how the Accounting Policy is set up and whether or not a site has written site-specific account validation code. Clients call this service when creating files, changing file ownership, or changing accounting information. If Account Validation is enabled, the Account Validation Service determines if the user is allowed to use a specific account or gives the user an account to use, if needed. The Core Server also calls this service to perform an authorization check just before account-sensitive operations take place.

•Location Server (LS). The Location Server acts as an information clearinghouse to its clients through the HPSS Client API to enable them to locate servers and gather information from both local and remote HPSS systems. Its primary function is to allow a client to determine a server's location and, by knowing other information about the server such as its object UUID, determine its server type or its subsystem id. This allows a client to contact the appropriate server. Usually the Location Server is only used by the Core Server or the Gatekeeper.

•Physical Volume Library (PVL). The PVL manages all HPSS physical volumes. It is in charge of mounting and dismounting sets of physical volumes, allocating drive and cartridge resources to satisfy mount and dismount requests, providing a mapping of physical volume to cartridge and of cartridge to Physical Volume Repository (PVR), and issuing commands to PVRs to perform physical mount and dismount actions. A primary function of the PVL is the support for atomic mounts of sets of cartridges for parallel access to data. Atomic mounts are implemented by the PVL, which waits until all necessary cartridge resources for a request are available before issuing mount commands to the PVRs.

HPSS Installation Guide	July 2008
Release 6.2 (Revision 2.0)	42