Sybase 12.4.2 Manuale Utente

Balancing I/O

 

This section explains how you can use the option Adaptive Server IQ provides 
to do disk striping, without using third party software. If you already have a 
disk striping solution through third party software and hardware, you should 
use it instead.

Turning disk striping 
on or off

The syntax you use to turn disk striping on or off is:

The default is 

ON

 for UNIX systems, and 

OFF

 for Windows NT systems. When 

disk striping is 

ON

, incoming data is spread across all dbspaces with space 

available. When disk striping is 

OFF

, dbspaces (disk segments) are filled up 

from the front on the logical file, filling one disk segment at a time.

As with all 

PUBLIC 

options, you must disconnect and then reconnect in order 

for the change to take effect.

When disk striping is on, you cannot drop dbspaces with the 

DROP DBSPACE

 

command. Since dbspaces are dropped as they are empty from last to first, and 
with this strategy dbspaces are filled partially in a more distributed manner, it 
is unlikely the dbspaces will be empty. If you want to be able to drop dbspaces, 
you should set 

DISK_STRIPING

 to 

OFF

.

Here are several different ways to think about distributing space on a large disk 
drive, for example 9GB:

1

Use different segments in different databases.

2

Mix them into the usage list with segments from different disk drives in 
between.

3

For the best multiuser performance, set your operating system or disk 
array to the maximum stripe size it supports.

Here is a good example: