IMPORTANT:
The libraries are NOT compatible with a high-voltage differential (HVD) SCSI bus. Do not put the library
on a narrow (50-pin) parallel SCSI bus because doing so will severely degrade performance.
If the host computer will have multiple parallel SCSI devices, you must decide how they will be configured into
one or more parallel SCSI buses.
About parallel SCSI buses
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 subaddresses, 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. HPE 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 the devices on the bus down to SE
speed. To see what kind of parallel SCSI interface a device has, see the interface specifications for the
device.
HBA requirements
For optimum performance, place each tape drive on its own parallel SCSI bus and use a host bus adapter
that can transfer data as fast as the library can read and write. Verify that the operating system supports the
HBA. For best performance, use an Ultra 320 HBA. For current HBA compatibility information, see the
compatibility matrix at:
http://www.hpe.com/storage/DAPRcompatability
.
IMPORTANT:
Do not connect an LTO tape drive to an SE SCSI bus, as it severely degrades library performance. A
single-ended SCSI host bus adapter severely degrades library performance and limits cable length.
Also, if any SE devices are on the SCSI bus, all the devices on the bus slow down to SE speed,
severely degrading performance.
Multiple LUN support
The library uses a single SCSI ID and two logical unit numbers (LUN). LUN 0 controls the tape drive and LUN
1 controls the robotic. The library requires an HBA that supports multiple LUNs. If multiple LUN support is not
enabled, the host computer cannot scan beyond LUN 0 to discover the library. It just sees the tape drive.
Parallel SCSI HPE Smart Array controllers, RAID controllers, and most on-board HBAs do not support
multiple LUNs. For current HBA compatibility information, see the compatibility matrix at
www.hpe.com/storage/DAPRcompatability
IMPORTANT:
The library requires an HBA that supports multiple LUNs, which is also called “LUN scanning.”
30
Installing the tape library
