Implementing IBM xSeries SANs
Planning a SAN
Installing a SAN is a relatively complex undertaking that requires proper planning. In this
chapter we discuss some the steps you should take before starting to construct your own
SAN. During the writing of this paper, we implemented a small SAN in our lab and we give
examples of our own planning steps in the hope that these will assist you with your own
First of all we look at the hardware that we used for our SAN. The discussion is intentionally
brief. If you require more details about the products to which we refer in this section, we highly
recommend Fibre Array Storage Technology, A FAStT Introduction, SG24-6246.
FAStT500 Storage Server
The FAStT500 Storage Server, shown in Figure 2-1 on page 10, is a 4U-high, dual Fibre
Channel RAID controller. Each controller has a 300 MHz AMD K6 processor with 256 MB of
cache, which can be upgraded to 512 MB. The FAStT500 has fiber connectivity all the way
from host to drives and supports 1 Gbps transfer rates. Each controller has a serial
connection and a 10/100 Mbps Ethernet port for management.
The FAStT500 supports four host-side mini-hubs and another four mini-hubs for connections
to drive enclosures. On the drive side, each mini-hub supports a single loop. Two mini-hubs
provide a single FC-AL loop with redundancy, and the full complement of four mini-hubs can
therefore support two redundant loops.
A single Fibre Channel loop can support 126 devices. However, since each EXP500 external
disk enclosure houses 10 drives, all of which require an ID, and a management chip, which
also uses an ID, a total of 11 enclosures, using 121 IDs, can be attached to a loop. The total
number of drives supported by two loops is therefore 220.
FAStT EXP500 Storage Expansion Unit
The EXP500 is a 3U external rack-mountable storage enclosure which supports a maximum
of 10 Fibre Channel disk drives. The rear of the enclosure has two Enclosure Services
Monitor (ESM) boards. These boards have LEDs to indicate errors and events. The ESM
boards also have Tray ID switches. These switches need to be set to identify the enclosure
when multiple units are attached to a FAStT Storage Server.
The EXP500 has a SCSI Access Fault Tolerant Enclosure (SAF-TE) chip, which is a
management device that is used for monitoring and management of both the enclosure and
the drives it contains. A storage enclosure fault could be, for example, a fan failure or a high
SAN Fibre Channel switches
IBM offers two SAN Fibre Channel switches, the 2109 Models S16 and S08. Common
features of these switches are that they both have hot-swappable redundant power supplies
and cooling fans, and both have an RJ-45 connector supporting 10/100 Ethernet connections.
This port allows remote telnet and Web access for configuration, monitoring and testing of the
Both models also run the same fabric operating system, which allows the interconnection of
switches to create a SAN with hundreds of ports, providing high performance, scalability and
Differences between the switches are that the S16 is a 2U high device with 16 ports. The S16
also has an LED panel and a keypad, which are used to configure an IP address to allow you
to use a Web browser and JAVA for management.
In contrast, the S08 is a 1U high device that has eight ports. A terminal emulation program,
such as HyperTerminal, is used to perform IP address configuration over a serial port
connection. This allows you to use a Web browser and JAVA for management
FAStT Host Bus Adapter
The FAStT Host Bus Adapter is a 64-bit PCI adapter that can run at 66 MHz. The card is
backward compatible and can work in a PCI slot that is 32 bit and 33 MHz speed. This
adapter supports only short-wave Fibre Channel connections, since the GBIC is fixed.
The adapter is compliant with PCI Version 2.2 and Fibre Channel-Arbitrated Loop (FC-AL-2)
standards, and supports point-to-point and fabric connections. It support Fibre Channel to
SCSI and IP protocols, but only Fibre Channel to SCSI is supported in xSeries server
Power on and off sequence
The following procedure must be followed when applying or removing power to an xSeries
SAN solution. The FAStT500 controllers require that the attached EXP500 storage units are
powered on before power is applied to the FAStT500 Storage Server. This is due to the
controllers’ configuration being stored on the drives themselves, and is specific to the Tray IDs
and Slot IDs of the attached EXP500 storage units.
The recommended power-on procedure is:
1. Apply power to your EXP500 storage units
2. Apply power to your Fibre Channel hubs or switches
3. Apply power to your FAStT500 Storage Server
4. Apply power to your servers
The recommended power-off procedure is:
1. Remove power from your servers.
2. Remove power from your FAStT500 Storage Server
3. Remove power from your Fibre Channel hubs or switches
4. Remove power from your EXP500 storage units
FAStT Host Bus Adapter installation
The latest code versions are available from:
At the time we wrote this paper, you could download the code by following these steps:
1. From the list of systems below the Browse heading, click Servers to go to the xSeries
support home page.
2. In the Family listbox, select Fibre Channel Solutions to go to the Fibre Channel Solutions
3. On the left-hand navigator, click Downloadable files.
4. In the Downloadable files by category listbox, select Fibre Channel Solutions and you
will get a listing of all Fibre Channel files