Air Cleaner User Manual

Appendix E. Device/System-Specific Information
This chapter provides various notes and tips for using SysBack with various types
of devices, networks, or systems. The devices described in this chapter are not the
full list of devices supported by SysBack. The information provided here is specific
to devices or systems commonly used with SysBack, in which the performance or
usability might be impacted by the configuration of SysBack, the device, or the
system itself.
IBM 7208 8mm Tape Drives
All of the 7208 8mm tape drive models use a physical hardware blocking factor of
1024 bytes. This does not prevent the tape drive block size from being set to 512
bytes, but doing so causes the remaining 512 bytes of each physical block to go
unused. Therefore, half of the tape capacity, and up to half of the backup
performance, is lost if the tape block size is set to 512 bytes.
For best performance, the tape block size should be set to 1024 bytes,orany
multiple thereof.
IBM 3490, Magstar
®
, DLT and LTO Tape Drives
These are very high performance tape drives and contain a very large data buffer.
To achieve their highest throughput, send data to the tape drive’s buffer in very
large blocks. To do so, set the Buffer Size to 256 Kbytes when performing any
SysBack backup. Change the block size of the tape drive to either 0 or 262144 (256
Kbytes) using the Change Tape Drive Characteristics option. Doing so helps
ensure the drive continues streaming data without having to stop and wait for
additional data from the system. You can set the buffer size to a higher value as
long as the value is a multiple of the tape drive’s block size.
Note: Examples of drives in these categories are the IBM 3490, 3590, 3570, 3575,
7205, 7337, 3580, 3581, 3583, 3584., and third party DLT drives. You should
check with your vendor to determine if your drive benefits from using large
blocks.
Note that increased performance of the tape drive does not necessarily result in
faster backups if the data being backed up cannot be read at the same rate the tape
drive is writing. In many cases, reading fragmented data from a filesystem on even
the fastest disk drive can have trouble keeping up with the write performance of
these tape drives. To achieve the best performance, read performance of the disk
drives can be increased by keeping data contiguous on the disk and striping data
across multiple disks to spread the I/O workload evenly across multiple devices.
The settings and recommendations are not specific to SysBack. They are attributes
of the device driver and affect other commands that use the drives, such as tar, or
mksysb.
Also, make sure the tape drive Autoload feature is set to “no.” You can change this
feature using the Change Tape Drive Characteristics option. If this option is set to
“yes,” the loader changes tapes automatically, making the entire set of tapes
appear like a single tape to SysBack. Instead, turn this option off so that SysBack
handles the tape changes, placing a new volume label on each tape. It is absolutely
© Copyright IBM Corp. 2002,2003 E-1