Datasheet

address was changed with the device powered ON.
In general the SCSI adapter will be set at SCSI address of 7, but this is not always the case, so it is best to determine the
SCSI address of the SCSI adapter.
To determine the SCSI adapters in the system do the following AIX command:
lsdev -C | grep scsi
The output will be:
scsi0 Available 00-04 SCSI I/O Controller
To be sure of the SCSI adapter address do the following AIX command for the adapter you are going to attach to:
lsattr -El scsi0 | grep id
The output will be:
id 7 Adapter card SCSI ID
Note: High Availability(HA) systems often use 5 and 6 as the SCSI adapter address. Some systems restrict the SCSI
address, refer to your system manuals to determine any system restrictions.
To be sure of the addresses of other devices are already using on the SCSI bus do the AIX command:
lsdev -Cs scsi
Valid SCSI addresses for Narrow devices(8 bit) are 0 thru 7, with 7 usually reserved for the SCSI adapter.
Valid SCSI addresses for Wide devices(16 bit) are 0 thru 15 with 7 usually reserved for the SCSI adapter. When a Wide
device is attached to a narrow bus the available addresses are the same as if the device was a narrow device.
Note: On systems that use the Common Hardware Reference Platform(CHRP), the SCSI address 15 may be used for CHRP
address. The backplanes use this address on CHRP boxes to ID backplane FRU locations codes in CHRP Error logs. The ID
15 is hard wired into the I-35 backplane. Any devices tagged with a SCSI address of 15 and attached to the SCSI interface
used by the backplanes are going to have a conflict of address, so if in doubt don't use the SCSI address of 15. Some systems
use more than 1 CHRP and use more than 1 SCSI address on the same SCSI adapter.. Currently the F50, H50, S70, and SP2
equivalents use CHRP.
The lsdev -Cs scsi command will show the following(adapter ID will vary):
ses0 10-68-00-15,0 SCSI-Enclosure Services Device
There may be multiple SCSI adapters in the system an each may have a SCSI-Enclosure Services Device at address 15.
Tape Drive Performance
The following information applies to most AIX tools(tar, cpio, backup, restore, dd, etc..) used to write or read data from
tape, backup and restore are used as generic names only.
Customers backing up the same size data or restoring data can find that the amount of time it takes to backup/restore data
may vary from backup to backup or restore to restore. Most tape drives work best when the tape drive can keep the tape
moving at a constant speed(streaming). The more the tape drive is able to keep the tape streaming the shorter the
backup/restore time will be. The ability of the tape drive to keep the tape streaming is effected by many factors.
These factors include:
z Tape drive rated performance.
z System performance, fast vs slower system. .
z System activity can often effect the time it takes to do a backup/restore. Backup/restore are best done during periods
of low system activity to reduce the impact on other system operations and on the backup/restore operation. Make
sure the backup is not done with other system activity that could effect the ability of the system to deliver the data to
the tape drive. Such as other devices on the SCSI bus with high activity, or other system activity.
z SCSI bus Activity on either the SCSI bus with the disks or the SCSI bus with the tape drives. High activity on either
SCSI bus may effect the ability of the system to keep the tape drive streaming.
z Some tape drives, when used on an AIX system, may provide the best performance when written to in the fixed block
mode. If your application writes tapes in variable blocked mode, you may find that by changing your application to
write in fixed block mode your backup or restore may take less time. It is recommended that if you are currently using
variable blocked mode you try changing your backup to a fixed block mode and compare the backup and restore time
Page 87 of 93Tape Help Package
5/20/2008file://C:\tem
p
\TAPEWHDR.html