Specifications

Introduction 3
• External SCSI Enclosures
– SCSI Multi-Storage Enclosure 3517 7-bay mini-tower enclosure (five
half-high hot-swap bays)
– PC Server Enterprise Expansion Enclosure 3518 22-bay tower enclosure
(18 slim-line hot-swap bays)
– PC Server Rack Storage Expansion Enclosure 3519 9-bay rack mounted
enclosure (six slim-line hot-swap bays)
– Netfinity EXP10 Storage Expansion Unit 3520 10-bay rack mounted
enclosure (10 half-high hot-swap bays)
• Differential Solution
– Symbios Logic MetaStor DS/RM-20E with the Symbios Logic PCI Ultra
SCSI Differential Controller SYM8751D
Note: The Symbios Logic MetaStor DS/RM-20E is only supported with the
Netfinity 7000 and the PC Server 704 for SAP R/3.
For detailed information on the range, please review
IBM PC Server Technology
and Selection Guide,
SG24-4760.
1.1.1.4 SSA Controller and Subsystems
Serial Storage Architecture (SSA) is a high-performance serial industry-standard
interface and is defined to connect devices to host adapters. It is specified
through the open ANSI standard X3T10.1 and includes SCSI-2 commands,
queuing model, status, and sense bytes. The current maximum transfer rate is 80
MBps and IBM is developing devices with transfer rates of 160 MBps.
SSA subsystems are typically built up by bidirectional loops of adapters and
devices. SSA is a point-to-point serial link without the disadvantages of a bus
system such as SCSI. Therefore, SSA does not use bus arbitration for
communication. A dual-port SSA host allows four conversations. Bus
architectures can have only a single conversation at the same time. Each port
supports a 20 MBps read and a 20 MBps write. A dual-port adapter using
full-duplex capability can have a bandwidth of 80 MBps. You can achieve
sustained data rates as high as 60 MBps in non-RAID mode and 35 MBps in
RAID mode.
For your SAP R/3 environment, we recommend you use only the RAID
adapters to implement RAID technology with high-performance and data
availability. The common SCSI adapters are very useful for connecting
backup devices or for smaller test-and-development environments to
build software RAID systems.
The supported maximum number of PC ServeRAID II SCSI Adapters you
can use in any one server is five. As the ServeRAID Adapter is a
full-sized PCI adapter, you can only use PCI slots that can accept
full-sized adapters.
Note