Chapter 2 HPSS Planning
116 September 2002 HPSS Installation Guide
Release 4.5, Revision 2
Expect both the disk storage segment metadata file and the disk storage map metadata file to be
quite volatile. As files are added to HPSS, disk storage segments will be created, and as files are
migrated to tape and purged from disk, they will be deleted. If SFS storage is available on a
selectionof devices, the disk storage segment metadata file and the storage disk map file would be
good candidates for placement on the fastest device of suitable size.
SS Disk Physical Volumes. The disk PV metadata file describes each disk partition or logical
volume imported into HPSS. There will be at least one partition for each disk device managed by
HPSS, and there is one record in this SFS file for each partition.
SS Disk Virtual Volumes. The disk VV metadata file describes all disk virtual volumes created by
this Storage Server. Each VV is described by a separate record in this file.
2.10.2.7 Tape Storage Server Metadata
The Tape Storage Server is the primary user of the following SFS metadata files (the default SFS
filenames are shown in parentheses):
• SS Tape Storage Maps (storagemaptape.#)
• SS Tape Storage Segments (storagesegtape.#)
• SS Tape Physical Volumes (sspvtape.#)
• SS Tape Virtual Volumes (vvtape.#)
EachTape Storage Server requires its own set of fourmetadata storage files: one file for tape storage
maps,one for tape storage segment metadata records, one for virtual volume metadata records and
onefor physical volume metadata records. If a system has more than one Tape Storage Server,each
server must have its own set of files. Files must not be shared between servers.
SS Tape Storage Maps. This metadata file is used to track the allocation of storage on tape virtual
volumes. The number of tape storage map records should be equal to the number of tape virtual
volumes plus the number of tape storage classes because a special map record is used to track
statistics for each tape storage class.
SS Tape Storage Segments. The tape storage segment metadata file may become large. Storage
segments are created by the server to describe contiguouschunks of data written on tapes. Some
segmentsmay be long but others may be short. The number of storage segments found on a given
tape is not limited by the server. This number is a function of the length of the files written on the
tape, the VV block size, the size of the data buffer used to write the tape, and other factors.
Whilethe size of the tape metadata files may become large as the tape system grows, the volatility
of the tape metadata files is low. PV and VV metadata records are created and deleted only when
tapes are added to and removed from the system. These records are modified only when the
associated tapes are read or written, so most records will remain unchanged for long periods of
time. Most storage segment and storage map metadata records are created and/or modified only
asthe associated tapes are written. The volatility of these files is a function of the rate at which files
are written to tape, but compared to a Disk Storage Server, a Tape Storage Server's metadata files
are relatively static. Therefore, larger, possibly slower, disk systems would be good candidates to
assign to SFS for the storage of Tape Storage Server metadata files.