Sybase 12.4.2 User Manual

CHAPTER 12    Managing System Resources

 Here are some general rules on disk striping:

•

For maximum performance, the individual disks in a striped file system 
should be spread out across several disk controllers. But be careful not to 
saturate a disk controller with too many disks. Typically, most SCSI 
machines can handle 2–3 disks per controller. See your hardware 
documentation for more information.

•

Do not put disks on the same controller as slower devices, such as tape 
drives or CD-ROMs. This slows down the disk controller.

•

Allocate 4 disks per server CPU in the strip.

•

The individual disks must be identical devices. This means they must be 
the same size, have the same format, and often be the same brand. If the 
layouts are different, then the size of the smallest one is often used and 
other disk space is wasted. Also, the speed of the slowest disk is often 
used.

•

In general, disks used for file striping should not be used for any other 
purpose. For example, do not use a file striped disk as a swap partition.

•

Never use the disk containing the root file system as part of a striped 
device.

In general, you should use disk striping whenever possible. 

For the best results when loading data, dump the data to a flat file located 

on a striped disk and then read the data into Adaptive Server IQ with the 

LOAD 

TABLE

 command.

Adaptive Server IQ stores its information in a series of dbspaces—files or raw 
partitions of a device—in blocks. Assuming that disk striping is in use, 
Adaptive Server IQ spreads data across data across all dbspaces that have space 
available. This approach lets you take advantage of multiple disk spindles at 
once, and provides the speed of parallel disk writes.