bytes.
Disk Storage Segments. (STORAGESEGDISK) Expect the size of the disk storage segment metadata table 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. A rough estimate of the number of disk storage segments can be obtained by estimating the number of files that will be resident on disk in the subsystem for each Storage Class, then multiplying by the Average Number of Segments parameter of the Storage Class.
Tape Storage Segments. (STORAGESEGTAPE) The tape storage segment metadata table grows as the number of files stored in the subsystem increases. Storage segments are created to describe contiguous chunks of data written on tapes. Segment sizes may vary greatly. The number of storage segments found on a given tape is not limited by the Core 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.
HPSS support representatives will help sites use this spreadsheet as they size the metadata disk resources and allocate those resources for the various DB2 tablespaces.
3.5.4.4. DB2 Disk Space
This section explains the local file system disk space requirements to support DB2, other than for database tables.
The disk space that DB2 requires falls into the following categories:
DB2 log
The DB2 log requires a filesystem in which transaction log files are stored. The number of log files and size of the files is controlled by several database configuration parameters. LOGFILSIZ determines the size of each log file and LOGPRIMARY + LOGSECOND
determine the total number of log files that could exist in the logging filesystem that you specify with NEWLOGPATH. Each database should log to its own filesystem and must utilize a RAID device for storing the data. Also, it is required to use the DB2 MIRRORLOGPATH configuration variable and define a separate filesystem to store the mirrored log file.
When DB2 is first started, log files are placed in the /var/hpss/<instance_name>/NODE0000/...
directory. After DB2 is started, use the database configuration parameters NEWLOGPATH and MIRRORLOGPATH to direct log files to a prepared location.
To determine the amount of disk space required for the DB2 log files, run:
% db2 get db cfg for <db name>
Look for the LOGFILSIZ variable, which is the size of each log file, and multiply it by the total number of logs for this database (LOGPRIMARY + LOGSECOND). The result will be the number of 4KB blocks needed. To convert this to the number of bytes, multiply the result by 4096. Calculate this for each database that utilizes this particular log filesystem to determine the total necessary disk space.
The optimal type of disk used for the log filesystem(s) is a
DB2 database home directories
DB2 requires approximately 700MB of disk space for installation. Upon installation each database
HPSS Installation Guide | July 2008 |
Release 6.2 (Revision 2.0) | 77 |
