HP Surestore Disk Array FC60 HP SureStore E Disk Array 12H User's and Service - Page 270

Target, Terminator Block, Time Stamp, Unallocated Capacity, Uninterruptable Power Supply

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Glossary Glossary Target Terminator Block Time Stamp A SCSI device (usually the peripheral) that responds to an operation requested by a SCSI initiator (usually the host system). SCSI peripherals are targets, but for some commands (for example, a COPY command), the peripheral may need to act temporarily as an initiator. An electrical connection at each end of the SCSI bus composed of a set of resistors (or possibly other components). Its function is to provide a pull-up for open-collector drivers on the bus, and also impedance matching to prevent signal reflections at the ends of the cable. The SCSI bus requires termination at both ends of the bus. One end of the SCSI bus is terminated by the adapter's internal termination. The other end should have a terminator placed on the 68-pin high density SCSI connector on the last SCSI peripheral. If this device is not terminated, data errors may occur. All data blocks stored on the disk array are written along with a Time Stamp. The Time Stamp allows the Disk Array Controller to determine how frequently blocks of data have been accessed. Unallocated Capacity Array capacity that has not been assigned to a Logical Drive, and therefore is not available to the server. The disk array uses all Unallocated Capacity to improve array performance by using it for RAID 0/1 storage. Uninterruptable Power Supply An Uninterruptable Power Supply is a power supply that is capable of maintaining power even if the input ac mains supply loses its source of power. VEB VEB (Very Early Busy) is a SCSI parameter. VEB instructs the disk array to return a BUSY response during its power-on sequence. Following a power-on, it can take the disk array up to three minutes to complete its internal self-test sequence. During this time, the disk array will not respond to host commands if VEB is disabled. This may cause some host systems to time out while waiting for the disk array to respond. If VEB is enabled, the disk array will return a BUSY status to the host rather than simply ignore any commands during this interval. This will alert the host system to the presence of the disk array and thus avoid the possibility of the host system "timing out" before the disk array is ready. 270

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Glossary
270
Glossary
Target
A SCSI device (usually the peripheral) that responds to an operation
requested by a SCSI initiator (usually the host system). SCSI
peripherals are targets, but for some commands (for example, a COPY
command), the peripheral may need to act temporarily as an initiator.
Terminator Block
An electrical connection at each end of the SCSI bus composed of a set
of resistors (or possibly other components). Its function is to provide a
pull-up for open-collector drivers on the bus, and also impedance
matching to prevent signal reflections at the ends of the cable. The
SCSI bus requires termination at both ends of the bus. One end of the
SCSI bus is terminated by the adapter’s internal termination. The other
end should have a terminator placed on the 68-pin high density SCSI
connector on the last SCSI peripheral. If this device is not terminated,
data errors may occur.
Time Stamp
All data blocks stored on the disk array are written along with a Time
Stamp. The Time Stamp allows the
Disk Array Controller
to determine
how frequently blocks of data have been accessed.
Unallocated Capacity
Array capacity that has not been assigned to a
Logical
Drive
, and
therefore is not available to the server. The disk array uses all
Unallocated Capacity to improve array performance by using it for
RAID
0/1
storage.
Uninterruptable Power Supply
An Uninterruptable Power Supply is a power supply that is capable of
maintaining power even if the input ac mains supply loses its source of
power.
VEB
VEB (Very Early Busy) is a SCSI parameter. VEB instructs the disk
array to return a BUSY response during its power-on sequence.
Following a power-on, it can take the disk array up to three minutes to
complete its internal self-test sequence. During this time, the disk array
will not respond to host commands if VEB is disabled. This may cause
some host systems to time out while waiting for the disk array to
respond. If VEB is enabled, the disk array will return a BUSY status to
the host rather than simply ignore any commands during this interval.
This will alert the host system to the presence of the disk array and thus
avoid the possibility of the host system “timing out” before the disk
array is ready.