HP StoreEver MSL2024, MSL4048, MSL8048, and MSL8096 Tape Libraries User and Service Guide (AK378-96059, December 2012)

• Install application software and compatible drivers on the host computer. See the application
software manuals for installation and configuration information.
• For parallel SCSI libraries, make sure multiple LUN support is enabled on the HBA and
operating system. See “Multiple LUN support” (page 14).
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-4 tape drive must be on its own Ultra 320 SCSI 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.
• Avoid putting an SE SCSI device on the same bus as a tape drive because the SE device will
slow the tape drive to SE speed and reduce the allowable cable length.
SCSI addresses
NOTE: The HBA also has a SCSI address, which is typically 7.
Verify that each device on the bus has a unique SCSI address. If these pre-configured addresses
will not be unique on a bus, you will need to change the SCSI address of one or more of the tape
drives during the installation process.
Planning the parallel SCSI configuration 39