Installation guide

AIX - Installation Instructions-
22 Fourth Edition 96107
StorageTek Proprietary
■ Performance considerations
There are several parameters of the disk and HBA driver that affect
performance.
These are addressed in the odm database parameters. The ODM settings for
the storage system have already been set. See default settings in the example
below.
1. The osdisk (the default disk device type) ODM settings have default queue
type set to NONE and queue depth set to 1. The updated ODM settings
are type = SIMPLE and depth=255. These may be changed using lsattr
command to view and chdev command to modify these attributes. NOTE:
The relative effect of this parameter is limited by the controller, which is
independently capable of 512 concurrent I/Os. The combined pair with
mirrored cache, however, presents an array limitation of 768 concurrent I/
Os. You can display the current parameters for an hdisk with the lsattr
-El hdisk(n) command. You can display the current parameters for an
HBA with the lsattr -El fcs(n) command.
2. The default osdisk ODM settings set the cache mode pages in such a way
as to disable any read ahead caching and turn off write cache enable. The
updated ODM settings remove the cache mode changes.
3. The updated osdisk ODM adds the max_coalesce and max_transfer
attributes. The max_coalesce allows the scsi driver to coalesce large
sequential I/O into larger single I/O’s which helps performance on those
types of I/O patterns. The max_transfer allows tuning of the maximum size
of a transfer packet, with the default setting of 0x40000.