Filter
Top Products
Chapter 2 HPSS Planning
HPSS Installation Guide September 2002 113
Release 4.5, Revision 2
• Bitfile Tape Segments (bftapesegment.#)
• BFS Storage Segment Checkpoint (bfsssegchkpt.#)
• BFS Storage Segment Unlinks (bfssunlink.#)
• Bitfile COS Changes (bfcoschange.#)
• Bitfile Migration Records (bfmigrrec.#)
• Bitfile Purge Records (bfpurgerec.#)
• Accounting Summary Records (acctsum)
• Accounting Logging Records (acctlog.#)
Storage Classes. One record is created in this metadata file for each storage class that is defined.
Space for 50 storage classes should generally be sufficient for metadata planning purposes.
Hierarchies. This metadata file defines the various storage hierarchies in HPSS. This number
generally will equal the COS record count. Planning for 25 to 50 hierarchies should be sufficient.
Classes of Service. The class of service metadata file records the definition of each COS. Space for
25 to 50 classes of service should be sufficient for planning purposes.
Bitfiles. For each bitfile in the system, a record is created in this metadata file. The amount of space
allocated for this SFS file will normally limit how many bitfiles can be created. Regardless of how
many copies of a bitfile exist and whether the bitfile is spread across disk and/or tape, only one
bitfile record is created for the file definition.
Bitfile Disk Segments. For a bitfile that is stored on disk, you will have one or more records in the
bitfile disk segment file. Because bitfile disk segments simply keep track of contiguous pieces of a
bitfile, there normally will be only one disk segment record needed to map the file.
To arrive at the best estimate of the number of records you need in the bitfile disk segment, bitfile
tape segment, and bitfile disk map files, you need to take into account the way you have set up your
classes of service and hierarchies. For example, suppose you set up a three-level hierarchy that has
disk at the top level and two levels of tape. The migration policy calls for creating duplicate copies
on tape. Assume that you have a 2 GB disk in the disk storage class and that the storage segment
size is 512K. The maximum number of disk storage segments that could be created in this case
would be 4,096. Thus you would need a maximum of 4,096 disk map records. Assume that you also
plan to store 100,000 files in this hierarchy. You will have two tape copies for each file. Assuming
an average of 2 bitfile tape segment records per file, you would end up creating 400,000 bitfile tape
segment records. You may not have this level of detail, but the more you know, the more accurate
your estimates can be.
Bitfile Disk Allocation Maps. Also for disk files, one or more records will be created in the disk
map file. The number of these records is determined by the storage segment size in the storage class
in which the files are to be stored and the average file sizes to be stored in that storage class. It is
generally recommended that the average number of storage segments per file (which is the average
file size divided by the storage segment size) be 10 or less.
A single disk allocation map can hold up to eight storage segments. For planning purposes, you
can assume two segments per disk file, on average, such that the total number of disk allocation