• For SAS Tape Libraries, install a SAS host bus adapter (HBA) with an external SAS connector that
supports multiple LUNs. Refer to the manuals for the host computer and the HBA for installation
information. See “Planning the SAS configuration” on page 40 for configuration requirements.
• For Fibre Channel Tape Libraries, install an FC host bus adapter (HBA) or verify that you have
sufficient ports available on a compatible Fibre Channel switch. See “Planning the Fibre Channel
configuration” on page 41 for configuration requirements.
• Install application software and compatible drivers on the host computer. See the application
software manuals for installation and configuration information.
• For parallel SCSI devices, make sure multiple LUN support is enabled on the HBA and operating
system. See “Multiple LUN support” on page 23.
Planning the parallel SCSI configuration
If the host computer will have multiple parallel SCSI devices, you must decide how they will be
configured into one or more parallel SCSI busses.
About parallel SCSI busses
A parallel SCSI bus consists of the host bus adapter (HBA), the parallel SCSI devices, the parallel
SCSI cables, and the terminators. The HBA and devices are connected in a chain, with each device
connected to the next. The last device must have a SCSI terminator. Each device in the chain must
have a unique SCSI address (SCSI ID).
Complex devices, such as the Library, assign sub-addresses, called logical unit numbers (LUNs), to
different parts of the device. The HBA and operating system must support multiple LUNs, also called
LUN scanning, for the application software to operate the Library. HP Smart Array controllers, most
third-party RAID controllers, and many on-board SCSI controllers do not support multiple LUNs.
An HBA might have one or two channels, with each channel supporting one parallel SCSI bus. Check
to see how many channels the HBA has and what devices are already connected to the HBA. Some
devices, such as parallel SCSI disk drives, could be inside the server.
The devices on a parallel SCSI bus share bandwidth so be careful about which devices you put
together on a bus. Also, putting a single-ended (SE) SCSI device on the bus will slow all of the devices
on the bus down to SE speed. Check each device's interface specifications to see what kind of parallel
SCSI interface it has.
Optimizing throughput
If possible, put each tape drive on its own parallel SCSI bus. For optimum performance, each LTO-3
or LTO-4 tape drive must be on its own Ultra 320 SCSI bus. Two LTO-2 tape drives can share an Ultra
320 SCSI bus or each tape drive can be on its own Ultra 160 bus. This will give you the best
performance and easiest installation.
If a tape drive must share a parallel SCSI bus with one or more other devices or the Library has multiple
tape drives that must share a bus, follow these guidelines to plan your parallel SCSI busses for the
highest performance:
• Do not put a tape drive on the same parallel SCSI bus as a disk drive because the system and
backup performance will be slow when data is written from the hard drive to tape or from tape
to the hard drive.
• Do not put a tape drive on the same parallel SCSI bus as a disk array because the disk and the
tape drive performance will be affected, most RAID controllers do not support multiple LUNs, and
the data on the disk array could become corrupted.
Installing the Tape Library38
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