IBM High Performance Storage System HPSS, Руководство по установке

Страница: 42 / 311

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