Specifications

2 Optimizing IBM Netfinity Servers for SAP R/3 and Windows NT
1.1.1.1 Disk Space for SAP R/3
The SAP R/3 system is a data-intensive application with huge databases and
demands unusually large amounts of disk storage. It transfers massive blocks of
information so you will need a technology that is robust, reliable and scalable. You
have a huge choice of internal and external hard disk subsystems for best
performance and data reliability. The available solutions are divided into two
different storage system interfaces that define the connection between a hard
drive or storage subsystem and the computer.
1.1.1.2 SCSI Controller and Subsystems
A Small Computer Systems Interface (SCSI) controller has its own bus and set of
instructions. There are several SCSI standards defined that differ in the used data
transfer rate, the clock rate and the data path width on the SCSI bus. We talk only
about SCSI-2 Fast/Wide and SCSI-2 Ultra Fast/Wide, because the Netfinity
servers and the expansion enclosures are enabled either for one or both of these.
Up to 15 SCSI devices can be attached to a single SCSI-2 Fast/Wide or SCSI-2
Ultra Fast/Wide bus, which includes the SCSI controller as a SCSI device. One of
the SCSI disadvantages is the bus arbitration, which means only two of those
devices can communicate with each other at one time.
A problem of high clock rates on the SCSI bus is the possible cable length. With
single-ended SCSI over long distances at a high clocking rate the signal can
degrade and errors can occur. Differential SCSI was developed to solve this.
The bus length of SCSI-2 Ultra Fast/Wide is restricted to 1.5 meters. With
differential SCSI, longer cable lengths can be maintained, up to 25 meters. IBM
provided the differential SCSI solution: MetaStor RM/DS-20E from Symbios
Logic, an external redundant array of independent disks (RAID) subsystem,
which is connected to the server over a differential SCSI controller.
For more detailed information about SCSI and RAID technology see
Implementing PC ServeRAID SCSI and SSA RAID Disk Subsystems,
SG24-2098.
IBM offers Ultra Fast/Wide SCSI adapters and Ultra Fast/Wide SCSI RAID
adapters to control and extend your internal disk space and hold your data. The
RAID adapters provide high-performance hardware implementation of RAID-0,
RAID-1, Advanced RAID-1 and RAID-5.
1.1.1.3 SCSI Solutions for SAP R/3
• SCSI Adapters
– Two onboard Ultra Fast/Wide SCSI PCI Adapter in the Netfinity 7000
– One onboard Ultra Fast/Wide SCSI PCI Adapter in the PC Server 325 and
PC Server 330
– IBM ServeRAID II three-channel Ultra SCSI RAID Adapter
– Onboard IBM ServeRAID II one channel Ultra SCSI RAID Adapter in the
PC Server 330