IBM DS4000 EXP810, Installation, User'S, And Maintenance Manual

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Attention: The EXP810 storage expansion enclosure drive channel operates at
either 2 or 4 Gbps fibre channel interface speed. The EXP810 SATA E-DDM CRUs
have an ATA translator card that converts E-DDM 3 Gbps SATA drive interface
protocol to either 2 Gbps or 4 Gbps fibre channel interface protocol. It is
recommended that the EXP810 enclosure speed is set to 4 Gbps when these SATA
E-DDM CRUs are installed and connected to storage expansion enclosures running
at 4 Gbps speed. The Link Rate setting speed must be set accordingly. See
“Verifying the Link Rate setting ” on page 101 for more information. The enclosure
speed of the DS4000 storage subsystem that the EXP810s are connected to must
also be set to 4 Gbps.
Attention
Before you power on a DS4000 storage subsystem without any internal drive
slots, the DS4000 must be cabled to at least one storage expansion enclosure
populated with at least two E-DDMs. If at least two E-DDMs are not installed
in each attached storage expansion enclosure when you power on the
DS4000 storage subsystem, your standard storage partition key will be lost
and will need to be regenerated using instructions on the IBM DS4000
Solutions and Premium Features Web site:
https://www-912.ibm.com/PremiumFeatures/
Additionally, if at least two E-DDMs are not installed in each attached storage
expansion enclosure, the resulting insufficient load to the storage expansion
enclosure power supply CRUs might cause the storage expansion enclosure
power supply CRUs to intermittently appear as failed and then reappear in an
optimal state, falsely indicating that the power supply CRUs are bad.
Figure 48 on page 89 shows an example of a DS4000 storage subsystem
configured with redundant drive loop pairs.
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IBM System Storage DS4000 EXP810 Storage Expansion Enclosure: Installation, User’s and Maintenance Guide