Table of Contents
Advertisement
Chapter 2
HPSS Planning
volume to use in allocating this disk space. An integer value from 1 to 10 can be entered. For
example, if four AIX logical volumes are allocated to SFS, use values from 1 to 4 to assign each
metadata file to the appropriate volume. The Space Allocation Per Encina Volume table, located on the
same worksheet, will use this allocation to calculate total disk space requirements per SFS volume.
By varying the SFS volume number, the administrator can experiment with how to best allocate the
metadata files based on the logical volume sizes.
It is important to note that calculating the size of an SFS balanced-tree file is not easy and is
sometimes inaccurate. The file sizes do not grow linearly according to the number of records
because of the changing height of the B-tree and the fact that leaf pages may not be full. In this
spreadsheet, the maximum height of the B-tree is calculated based on the order of the B-tree and
the number of records. In other words, the spreadsheet assumes a worst case, which is appropriate
when planning disk space requirements.
For more information on how the size of SFS B-trees can be calculated, refer to Encina Overview, an
IBM ITSO Redbook (GG24-2512-00).
Secondary Index 1—This section shows the disk space requirement for the first secondary index
associated with each metadata file, if such an index is used. The SFS Vol # column allows this disk
space to be allocated to a particular logical SFS volume. However, the managesfs utility used to
create HPSS metadata files currently creates the file and all associated indices on the same SFS
volume. So normally, the SFS volume columns in the spreadsheet will contain the same logical SFS
volume number for a given metadata file row.
If, for performance or disk-space limitation reasons, a secondary index is to be created on a different
SFS volume from the primary index, use managesfs to first create the metadata file specifying the
SFS volume desired for the primary data/index, manually delete the secondary index using the
sfsadmin command, and attempt to recreate the metadata file using managesfs while specifying
the SFS volume desired for the secondary index. The second attempt to create the metadata file will
yield an error indicating that the metadata file already exists; however, it will go ahead and recreate
the secondary index on the different SFS volume.
Secondary Index 2—This section shows the disk space requirement for the second secondary index
associated with each metadata file, if such an index is used.
Secondary Index 3—This section shows the disk space requirement for the third secondary index
associated with each metadata file, if such an index is used.
Total Size (MBs)—This column calculates, in megabytes, the sum of all disk space used for the
primary data and index, as well as all secondary indices.
Space Allocation Per Encina Volume—Continuing to the right on this worksheet, is another table that
summarizes the disk space allocation per logical SFS volume per metadata file. These calculations
are based on the SFS Vol numbers entered in the previous table. At the bottom of this table are the
overall totals for each SFS volume, in megabytes.
2.10.2.22 Encina SFS Disk Space
This section explains the disk space requirements of Encina, parts of which come from completing
the metadata sizing spreadsheet. The disk space used by Encina SFS falls into the following
categories:
130
September 2002
HPSS Installation Guide
Release 4.5, Revision 2
Advertisement
Table of Contents
