IBM DS3950, Installation, User'S, And Maintenance Manual, Page: 83 / 252

Connecting storage expansion enclosures to the DS3950
Attention: Before you turn on the power to the DS3950 storage subsystem, it
must be populated with at least two E-DDMs. If at least two E-DDMs are not
installed in the DS3950, an insufficient load to the enclosure power supplies might
cause them to intermittently appear as failed, falsely indicating the power supplies
are bad. All of the E-DDMs in the DS3950 storage subsystem and the connected
storage expansion enclosure or enclosures must contain no prior configuration
data.
In the initial installation of the DS3950, you can add only new storage expansion
enclosures to the DS3950 storage subsystem. This means there must be no existing
configuration information about the storage expansion enclosures that you want to
install.
The DS3950 supports the attachment of up to six EXP395 and EXP810 storage
expansion enclosures, resulting in the capability to connect up to 112 E-DDMs and
enabling storage configurations of over 67 TB using 600 GB Fibre Channel or
FC-SAS E-DDMs or 224 TB using 3 TB SATA E-DDMs.
The base DS3950 storage subsystem supports up to 32 drives, which includes 16
drives in the DS3950 chassis and 16 more drives in an attached storage expansion
enclosure. To attach more than 32 drives, you much purchase the applicable feature
option.
To attach additional drives to the DS3950, you can use EXP395 or EXP810 storage
expansion enclosures. You can connect EXP395 storage expansion enclosures to the
DS3950 without purchasing feature options. To attach an EXP810 storage expansion
enclosure or enclosures to the DS3950, you must purchase the Attach EXP810 to
DS3950 Activation feature option. Contact your IBM marketing representative or
IBM reseller for more information.
To connect 33 - 64 drives in one DS3950 and three EXP395 storage expansion
enclosures, you must purchase the DS3950 Drive Attach 33 - 64 feature option. If
you need to connect 65 - 112 drives in a DS3950 configuration, you must purchase
the DS3950 Drive Attach 65- 112 feature option in addition to the DS3950 Drive
Attach 33 - 64 feature option. These two feature options enable you to attach the
additional drives in one DS3950 and six EXP395/EXP810 storage expansion
enclosures. Contact your IBM marketing representative or IBM reseller for more
information.
If the storage expansion enclosures that you want to install currently contain
logical drives or configured hot spares, and you want them to be a part of the
DS3950 storage subsystem configuration, refer to the
IBM System Storage DS4000
Hard Drive and Storage Expansion Enclosure Installation and Migration Guide .
Improper drive migration might cause loss of configuration and other storage
subsystem problems. Contact your IBM technical support representative for
additional information.
Redundant drive channel pair
Each controller on the DS3950 has drive channel ports. The storage expansion
enclosures that are connected to these ports form a drive channel (also referred to
as drive loop). The maximum number of hard drives that can be installed in one
drive channel is 112. One drive channel from each controller combines to form a
redundant drive channel pair.
Chapter 3. Cabling the storage subsystem
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