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Cable requirements
SAS uses serial connections, with a direct connection between the host server and each of the
storage devices. This eliminates the need to configure SCSI busses and assign SCSI IDs, as is
required for parallel SCSI devices.
Most SAS HBA ports have four SAS channels. A tape drive uses one channel, so each HBA port
can support up to four tape drives. You can use a cable with one connector on each end, but
only one channel will be used. The SAS fanout cable recommended for use with the library can
connect up to four SAS tape drives to a single SAS HBA port. See
(page
24).
Figure 13 Example SAS fanout cable
Connectors
The host end of the cable must have the same type of connector as the HBA's external SAS
port.
The tape drive has a mini-SAS connector. The connector is keyed in location 4, which is the
standard location for end devices. If you use a cable other than the one recommended for use
with the product, verify that it is keyed in location 4.
CAUTION:
into the tape drive mini-SAS port because it might be keyed differently.
CAUTION:
Always verify that the SAS cable is rated for the data transfer speed of the HBA and tape
drive.
Do not use adapters or converters between the HBA and the tape drive. SAS signal rates
require clean connections and a minimum number of connections between the HBA and the
tape drive.
SAS cables described as "equalized" might not support 6 Gb/s data rates and should not
be used with LTO-5 or later generation tape drives unless these cables are verified for 6
Gb/s data rates.
For optimal performance, only use cables of the length specified as qualified for your products.
Do not use a SAS cable longer than 6 meters.
World Wide identifiers
A SAS tape drive is identified by a unique identifier called a World Wide Name (WWN) or World
Wide Identifier (WWID). The library assigns the World Wide identifier to the drive bay. When a
tape drive is replaced, the World Wide identifier is re-assigned to the new tape drive.
The operating system tracks the World Wide identifier for the drive on each HBA channel. Each
of the drive connectors on a fanout cable is associated with an HBA channel. Once a drive has
24
Installing the tape library
Mini-SAS connectors are keyed. Do not force a SAS cable's mini-SAS connector
Reliable data transfer requires high-quality cables and connections.
"Example SAS fanout cable"

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