HP Surestore 125ex Hewlett-Packard SureStore 125ex Optical Jukebox User&#1 - Page 104

Ukebox

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B NEXT PREVIOUS JUMP CONTENTS INDEX OPERATING THIS JUKEBOX ON A SCSI BUS THE SCSI BUS AND THIS JUKEBOX This jukebox is a "fast and narrow" SCSI device that uses either a single-ended or low-voltage differential external SCSI bus. The external connectors on the jukebox are "wide" (68-pin) but, because the internal SCSI bus in the jukebox is "narrow," only eight data lines are available for addressing. The jukebox may only use SCSI IDs from 0-8 (not 0-15 available on "wide" buses). The jukebox does not support logical unit number (LUN) addressing. When calculating available cable length, subtract 16 inches (0.41 metre), the length of the SCSI bus used internally by the jukebox. When considering adding other peripherals to the jukebox bus, you should consider the following: • Will adding a device onto a bus with this jukebox interfere or degrade the performance of the jukebox or the device that is added? • If the decision is made to add other devices to the jukebox bus, what SCSI requirements must be observed to make sure the bus will work? Before addressing some questions involved in deciding whether to place another device on the jukebox bus, we can say that, as a general rule, HP recommends that the jukebox be the only device on a bus. If there are multiple devices on the bus, performance of one or all of the devices on the bus can be affected. If you are still considering adding a device, you might first consider the quantity of data that the bus will have to carry, the frequency of data transfer, and the priority of this data transfer in your business. If you are using the jukebox as a backup or archive device, the demands on the jukebox will be different than if the jukebox is used for near-online storage where requests are more random in both frequency and data size. If you expect to be using the jukebox in the same time-frame as the other device, or devices, this might indicate that you may experience a drop in performance. 9

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B
O
PERATING
T
HIS
J
UKEBOX
ON
A
SCSI B
US
B
9
NEXT
PREVIOUS
JUMP
CONTENTS
INDEX
T
HE
SCSI B
US
AND
T
HIS
J
UKEBOX
This jukebox is a “fast and narrow” SCSI device that uses either a single-ended or low-voltage differential external
SCSI bus. The external connectors on the jukebox are “wide” (68-pin) but, because the internal SCSI bus in the jukebox
is “narrow,” only eight data lines are available for addressing. The jukebox may only use SCSI IDs from 0-8 (not 0-15
available on “wide” buses). The jukebox does not support logical unit number (LUN) addressing.
When calculating available cable length, subtract 16 inches (0.41 metre), the length of the SCSI bus used internally by
the jukebox.
When considering adding other peripherals to the jukebox bus, you should consider the following:
•
Will adding a device onto a bus with this jukebox interfere or degrade the performance of the jukebox or the device
that is added?
•
If the decision is made to add other devices to the jukebox bus, what SCSI requirements must be observed to make
sure the bus will work?
Before addressing some questions involved in deciding whether to place another device on the jukebox bus, we can say
that, as a general rule,
HP recommends that the jukebox be the only device on a bus. If there are multiple devices on
the bus, performance of one or all of the devices on the bus can be affected.
If you are still considering adding a device, you might first consider the quantity of data that the bus will have to carry,
the frequency of data transfer, and the priority of this data transfer in your business. If you are using the jukebox as a
backup or archive device, the demands on the jukebox will be different than if the jukebox is used for near-online stor-
age where requests are more random in both frequency and data size. If you expect to be using the jukebox in the same
time-frame as the other device, or devices, this might indicate that you may experience a drop in performance.