Computer Drive User Manual

COS Change Retry Limit, Tape Dismount Delay, Tape Handoff Delay, PVL Max Connection Wait,
Fragment Trim Limit and Fragment Smallest Block can be changed in the Core Server while the
server is running by changing the value on this screen, updating the metadata, then re-initializing the
appropriate Core Server. The Core Server re-reads the metadata and changes its internal settings. The
changes take effect the next time the settings are used by the server. See Section 5.2.2: Reinitializing a
Server on page 154 for more information.
Changes made to the rest of the settings on this screen take effect the next time the server is started.
Field Descriptions
Root Fileset Name. Core Servers can create and support multiple filesets, but an initial fileset is
required for each Core Server. The Root Fileset Name designates which of these filesets will be used by
the Core Server to resolve the pathname “/” in the subsystem. Other filesets served by this Core Server,
or from other Core Servers in the HPSS system may be joined to this fileset by junctions.
Root Fileset ID. The Fileset ID of the fileset named in Root Fileset Name.
Maximum Open Bitfiles. The maximum number of bitfiles that can be open simultaneously.
Maximum Active I/O Requests. The maximum number of simultaneous I/O requests allowed.
Maximum Active Copy Requests. The maximum number of simultaneous copy requests allowed.
COS Change Retry Limit. This is the maximum number of attempts that will be made to change the
class of service of a file. If set to 0, COS change will continue to be attempted until it is successful. If a
positive value is provided, the COS change request will be dropped after it has failed the configured
number of times.
Tape Dismount Delay (seconds). The amount of time, in seconds, a mounted tape volume will remain
idle before being dismounted by the Core Server. Larger values may reduce undesirable tape
dismount/remount events, at the expense of lower tape drive utilization.
Tape Handoff Delay (seconds). The amount of time, in seconds, a mounted tape will be held in a
client's session before become eligible to be handed off to another client that wishes to use the tape.
PVL Max Connection Wait (seconds). The amount of time, in seconds, the Core Server will wait to
connect to the PVL before declaring an error in pending PVL jobs.
Fragment Trim Limit (clusters). Fragment Trim Limit sets the lower limit of the number of clusters
that will be trimmed from a disk segment extent, when the extent turns out to be longer than the needed
length. Larger values tend to reduce disk fragmentation, but at the expense of increased slack space.
Fragment Smallest Block. Fragment Smallest Block sets the boundary used to determine where to
remove excess clusters from allocations that have excess space. The smallest block returned to the free
space map from the excess space at the end of an extent will be this size or larger.
COS Copy to disk. If ON, all copy operations associated with COS changes should be directed to disk
if the hierarchy has a disk storage class at its top level. If OFF, COS changes are not automatically
copied to the disk level. If there is a tape level in the hierarchy, they will go there instead.
5.1.1.1. Additional Core Server Configuration
Certain aspects of the operation of the Core Server can be controlled by setting environment variables.
HPSS Management Guide November 2009
Release 7.3 (Revision 1.0) 97