Storage Subsystem Considerations; Storage Policy Considerations; Migration Policy; 1.Migration Policy For Disk - IBM High Performance Storage System HPSS Installation Manual

Variable
HPSS_SM_SRV_MAX_CONNECTIONS
* The SM attempts to throttle the connection attempts to other servers. It will attempt to reconnect
to each server every HPSS_SM_SRV_CONNECT_INTERVAL_MIN seconds until the number of
failures for that server has reached HPSS_SM_SRV_CONNECT_FAIL_COUNT. After the failure
count has been reached the SM will only try to reconnect to the server every
HPSS_SM_SRV_CONNECT_INTERVAL_MAX seconds until a successful connection is made at
which time the connection interval for the server will be set back to
HPSS_SM_SRV_CONNECT_INTERVAL_MIN.

3.8. Storage Subsystem Considerations

Storage subsystems are provided in HPSS for the purpose of increasing the scalability of the system,
particularly with respect to the Core Servers. An HPSS system consists of one or more subsystems,
and each subsystem contains its own Core Server. If multiple Core Servers are desired, this is
accomplished by configuring multiple subsystems.
Each subsystem uses a separate DB2 database. Adding a subsystem to an HPSS system means
adding an additional database that must be maintained and backed up.

3.9. Storage Policy Considerations

This section describes the various policies that control the operation of the HPSS system.

3.9.1. Migration Policy

The migration policy provides the capability for HPSS to copy (migrate) data from one level in a
hierarchy to one or more lower levels. The migration policy defines the amount of data and the
conditions under which it is migrated; however, the number of copies and the location of those copies
is determined by the storage hierarchy definition. The site administrator will need to monitor the
usage of the storage classes being migrated and adjust both the migration and purge policies to obtain
the desired results.
3.9.1.1. Migration Policy for Disk
Disk migration in HPSS copies (migrates) files from a disk storage class to one or more lower levels
in the storage hierarchy. Removing or purging of the files from disk storage class is controlled by the
purge policy. The migration and purge policies work in conjunction to maintain sufficient storage
space in the disk storage class.
When data is copied from the disk, the copied data will be marked purgeable but will not be deleted.
Data is deleted by running purge on the storage class. If duplicate copies are created, the copied data
is not marked purgeable until all copies have been successfully created. The migration policy and
purge policy associated with a disk storage class must be set up to provide sufficient free space to
deal with demand for storage. This involves setting the parameters in the migration policy to migrate
a sufficient number of files and setting the purge policy to reclaim enough of this disk space to
provide the free space desired for users of the disk storage class.
HPSS Installation Guide
Release 6.2 (Revision 2.0)
Default
Value
Number of HPSS server connections to
maintain at once. If this number of
connections is exceeded, then old
connections will be closed to maintain
50 this number of connections
July 2008
Functionality
94