Q40 Tape Library Installation and Operations Manual
511026 Rev. 07-01-19 20
3.3 SAS Configuration Requirements
Serial Attached SCSI (SAS) is a computer bus technology mainly used to transfer data to and from
storage devices, including disk drives and tape drives. SAS is designed to transfer data at up to 6 Gbps.
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.
The host server must have a SAS Host Bus Adapter (HBA) with an external connector. The HBA uses
multiple Logical Unit Numbers (LUNs) to communicate with the library. Verify that your HBA supports
multiple LUNs. Please note, most RAID controllers do not have multiple LUNs support. 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, or a fan-out cable, which has one
connector on one end and up to four connectors on the opposite end. Supported speeds by drive
generation are shown in the table below.
T
able 4: Supported SAS Speeds
LTO Generation Supported Speeds
LTO-6 1.5 Gbps, 3 Gbps, 6 Gbps
LTO-7 1.5 Gbps, 3 Gbps, 6 Gbps
LTO-8 1.5 Gbps, 3 Gbps, 6 Gbps
High quality SAS cables rated at the transfer rate of the SAS drives are
required. Always verify that the SAS cable you are using is rated for the
data transfer speed of the interface of your components. SAS cables
described as "equalized" may not support 6 Gb/s data rates and should
not be used with LTO-6 or later generation tape drives unless these
cables are verified for 6 Gb/s data rates.
The library has one or more mini-SAS connectors on each SAS tape
drive. Mini-SAS connectors are keyed. Do not force a SAS cable’s mini-
SAS connector into the tape drive as it might be keyed differently.
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 WWID to the drive bay. When a tape drive is replaced, the
WWID is re-assigned to the new tape drive.
The operating system tracks the WWID for the tape drive on each HBA channel. Each of the drive
connectors on the fan-out cable is associated with an HBA channel. Once a tape drive has been plugged
in, it should remain on the same channel to retain the association between the HBA channel and WWID.
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