Sybase 12.4.2 manual Internal striping, Recommendations for disk striping, 443

CHAPTER 12 Managing System Resources

Recommendations for disk striping

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.

Note 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.

Internal striping

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.

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