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Chapter 2 HPSS Planning
70 September 2002 HPSS Installation Guide
Release 4.5, Revision 2
requests from a particular host or user. The Site Interfaces will be located in a shared library that is
linked into the Gatekeeper Server.
It is important that the Site Interfaces return a status in a timely fashion. Create, open, and stage
requests from DFS, NFS, and MPS are timing sensitive, thus the Site Interfaces won't be permitted
to delay or deny these requests, however the Site Interfaces may choose to be involved in keeping
statistics on these requests by monitoring requests from Authorized Callers.
If a Gatekeeper Server should become heavily loaded, additional Gatekeeper Servers can be
configured (maximum of one Gatekeeper Server per storage subsystem). In order to keep the
Gatekeepers simple and fast, Gatekeeper Servers do not share state information. Thus if a site wrote
a policy to allow each host a maximum of 20 creates, then that host would be allowed to create 20
files on each storage subsystem that has a separate Gatekeeper Server.
The Gatekeeper Server Real Time Monitoring Interface supports clients such as a Real Time
Monitoring utility which requests information about particular user files or HPSS Request Ids.
2.6.7 Location Server
All HPSS client API applications, which includes all end user applications, will need to contact the
Location Server at least once during initialization and usually later during execution in order to
locate the appropriate servers to contact. If the Location Server is down for an extended length of
time, these applications will eventually give up retrying their requests and become non-
operational. To avoid letting the Location Server become a single point of failure, consider
replicating it, preferably on a different machine. If replicating the Location Server is not an option
or desirable, consider increasing the automatic restart count for failed servers in SSM. Since the
Location Server’s requests are short lived, and each client contacts it through a cache, performance
alone is not usually a reason to replicate the Location Server. Generally the only time a Location
Server should be replicated solely for performance reasons is if it is reporting heavy load conditions
to SSM.
If any server is down for an extended length of time it is important to mark the server as non-
executable within SSM. As long as a server is marked executable the Location Server continues to
advertise its location to clients which may try to contact it.
The Location Server must be reinitialized or recycled whenever the Location Policy or its server
configuration is modified, Note that it is not necessary to recycle the Location Server if an HPSS
server’s configuration is added, modified, or removed since this information is periodically reread.
When multiple HPSS systems are connected to each other, the Location Servers share server
information. If you are connecting multiple HPSS systems together you will need to tell the
Location Server how to locate the Location Servers at the remote HPSS systems. You will need to
add a record for each site to the Remote Sites metadata file. See Section 2.2.7.1: Cross Cell Access on
page 45 for more details.
2.6.8 PVL
The PVL is responsible for mounting and dismounting PVs (such as tape and magnetic disk) and
queuing mount requests when required drives and media are in use. The PVL usually receives
requests from Storage Server clients. The PVL accomplishes any physical movement of media that