Chapter 4. IBM System Storage DS3500 and EXP3500 Cabling 109
Figure 4-21 An example of a multi-host, multi-port and multi-fabric host configuration
Before you attach hosts to the storage subsystem, you should always ensure that the host
systems and host bus adapters (HBAs) are installed correctly and updated with the supported
firmware and drivers levels. The supported levels are documented in the readme files that
come with the version of DS3500 firmware and DS Storage Manager that you want to use.
4.8.1 SAS attachment
Host server SAS HBAs are used to connect to the DS3500 SAS ports. Each DS3500
controller can have up to four SAS host ports when you install the optional SAS host interface
adapter. When the optional SAS host interface adapter is installed, the DS3500 can support
up to 28 Blade Center hosts when attached to the SAS Connectivity Module for IBM Blade
Center and up to four hosts in a direct attached host environment.
Always use redundant host connections. The use of redundant host connections with a single
controller DS3500 storage subsystem is supported but limits the number of hosts to a
maximum of two if the optional SAS host card is installed in the DS3500.
SAS host attachment examples
In this section we show examples of SAS host attachment with single and dual controller
DS3500 storage subsystems.
Figure 4-22 on page 110 shows the simplest host attachment method: a single host server
with one SAS host bus adapter connecting to a single controller DS3500 storage subsystem.
General rule: Although the example shown in Figure 4-22 on page 110 is a valid
supported configuration, there is no redundancy of host side connections. Always use
redundant host side connections instead.
110 IBM System Storage DS3500 Introduction and Implementation Guide
Figure 4-22 A single host with one SAS connection to the DS3500
Figure 4-23 on page 111 shows a single host with two host adapters connected to a single
controller DS3500 storage subsystem. In this example there are redundant host side
connections.
Chapter 4. IBM System Storage DS3500 and EXP3500 Cabling 111
Figure 4-23 Single host with two SAS connections to a DS3500 storage subsystem
Figure 4-24 on page 112 shows a host server with two SAS host bus adapters connecting to
a dual controller DS3500 storage subsystem. This particular configuration has redundant
host side connections and redundant controllers in the DS3500 storage subsystem.
112 IBM System Storage DS3500 Introduction and Implementation Guide
Figure 4-24 Host attachment with two SAS host bus adapters and dual DS3500 controllers
Figure 4-25 on page 113 show two host servers, each with one SAS host adapter, connecting
to a single controller DS3500 storage subsystem. In this example, there are no redundant
paths and no redundant controller.
General rule: Although the example shown in Figure 4-25 on page 113 is a valid
supported configuration, it does not have redundancy of either host-side connections or
controllers. Always use redundant host connections.
Note: For a single controller DS3500 storage subsystem, you will need to install the
optional SAS host interface card in the controller to attach two hosts using redundant SAS
connections.
Chapter 4. IBM System Storage DS3500 and EXP3500 Cabling 113
Figure 4-25 Two hosts connected to a single controller DS3500 using single SAS host adapters
Figure 4-26 on page 114 shows a configuration with two hosts connected using redundant
SAS connections to a dual controller DS3500 storage subsystem. This is a good
configuration because it has redundant paths to redundant controllers.

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