IBM DS4700 manual Data transfer rates for drive modules

Attention: All devices on the loop must have the same data transfer rate, which means that you must set the link rate on the storage expansion enclosure to the same rate as the storage subsystem to which it is connected. Information about supported DS4000 storage subsystems can be obtained from the certified Compatibility Matrix, which can be found at the following Internet location:

www-1.ibm.com/servers/storage/disk/ds4000/interop-matrix.html

Table 50. Data transfer rates for drive modules

Link Rate
Switch	Storage Subsystem	Storage Subsystem with	Storage Subsystem with
Setting	with 2 GB Drives	4 GB Drives	Mixed Drives
2 Gbps	Drives function in 2	Drives work in 2 Gbps	All drives work in 2 Gbps
	Gbps mode.	mode.	mode.
4 Gbps	Drives do not come	Drives work in 4 Gbps	2 GB drives do not come
	online.	mode.	online.
			4 GB drives work in 4 Gbps
			mode.

Use the following procedure to check the current setting of the data transfer rate and change it, if necessary:

1.Complete the power-off sequence described in “Turning off the storage subsystem” on page 134 ensuring that the DS4000 storage subsystem is turned off before any attached storage expansion enclosures.

2.Locate the Link Rate indicator LEDs. Figure 112 on page 163 shows the location of the Link Rate indicator lights on the back of the storage subsystem.

162IBM System Storage DS4700 Express Storage Subsystem: Installation, User’s and Maintenance Guide