Specifications

Configuring the Hardware and Installing Windows NT 63
system I/O request size, and no read ahead to the end of the stripe unit size is
performed.
To obtain optimum values is nearly impossible in a multitasking environment with
many different applications, or when using SAP R/3, which has many different
modules and varying and often changing user requirements.You may test your
special environment for a long time and still hardly see a difference. Moreover, if
you want to change the stripe size, you have to reinstall your system.
On an SAP R/3 application server the most important factor is not actually the I/O
subsystem but the installed main memory and the used processors and server
board technology. On the other hand, the database server needs a fast I/O
subsystem but it is also a very varying situation. The access to database index
files is usually sequential and the access to the database or tables is then
random.
Therefore, the best compromise is to use a stripe unit size of 16 KB or leave the
default setting and see if the change of the read ahead option has any effect.
To change the stripe unit size and the read ahead option do the following:
1. Select 7. Advanced Functions in the in the ServeRAID adapter configuration
main menu.
2. Select 5. Change RAID Parameters.
Figure 31. Change RAID Parameters
3. The current setting is shown directly below the table description.
4. Make your choices using the cursor keys and press Enter.
5. Press Esc to go back in the configuration main menu.
The read ahead setting can be modified without destroying data in a logical
unit.
Data Will Not Be Lost