Server Subsystem Components And Selection Guidelines; Disk Subsystem; Scsi Specifications - HP ML570 - ProLiant - G2 Tuning Manual

Novell NetWare 6 performance tuning guidelines for ProLiant servers
server subsystem
components and
selection guidelines

disk subsystem

SCSI specifications

As stated earlier, the Ziff-Davis test suites were chosen. The decision to use the Ziff-Davis
Benchmark is because it is designed to mimic real-world user applications. Original
equipment manufacturers (OEMs) and personal computer (PC) magazine use the Ziff-Davis
test suites in their research publications. To obtain the latest copy, go to www.zdnet.com.
The IT professional or the system administrator is responsible for selecting which subsystem
components provide sufficient bandwidth for optimal overall server performance.
Once the server is selected, the appropriate NOS is chosen to leverage the server
hardware components. For instance, if a multiprocessor (MP) server is selected, then a
corresponding network operating system and applications that are MP-aware should be
used.
The following sections highlight examples of critical server subsystem components and how
the selection you make can dramatically affect server performance.
The disk subsystem consists of the disk and the controller. One of the functions of the disk
subsystem is to keep the memory or cache filled with useful data. Insufficient memory leads
to a low cache hit rate and slower user access time. When this occurs, performance
decreases. It is a known fact that disk response time is significantly slower than memory
response time.
The performance of the disk subsystem can therefore be affected by the components that
constitute the subsystem. There are several elements that makeup the disk subsystem (i.e.,
SCSI (small computer system interface), disk, controller, drivers, bus interface, etc.). The
following components are crucial during the selection process:
SCSI
disk
controller
SCSI technology
SCSI technology is a widely used standard for transferring data between the disk drive
and the SCSI controller. Many types of SCSI technology are currently available and the
one you chose can impact overall system performance. It is therefore recommended to
select the type with the highest speed your disk drive and controller can support. Table 1
lists the different types of SCSI standards currently available.
table 1. SCSI standard specifications
bus speed
SCSI standard
(MHz)
SCSI 5
SCSI-2 10
SCSI ultra 20
SCSI ultra2 40
SCSI ultra3 40
SCSI ultra4 80
50-pin narrow 68-pin wide
(8-bit) (16-bit)
5 MB / s
10 MB / s 20 MB / s
20 MB / s 40 MB / s
40 MB / s 80 MB / s
160 MB / s
320 MB / s
maximum cable
length
6 meters
3 meters
1.5 meters
12 meters (LVD)
12 meters (LVD)
12 meters (LVD)
5