Hitachi Ultrastar 15K450, Specifications

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Hitachi Ultrastar 15K450 (FC-AL) Hard Disk Drive Specification
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required to access the first Logical Block. After the initial seek, no further counter incrementing is performed for that com-
mand.
Note: The length of a seek as reported in page 30 may differ from expected results. The reason for this is that the drive exe-
cutes Idle Time Functions between operations of the drive. The seek operations that occur in Idle Time Functions are not
directly entered into page 30 seek counters but they change the length of the following seek. This is because after the Idle Time
Function is completed, the heads will not necessarily be in the same position as they were at the completion of the previous
command.
A buffer overrun or under run condition occurs when the Initiator does not transfer data to or from the Target data buffer fast
enough to keep up with reading or writing the media. The buffer overrun counter is incremented during operations that require
a Data In phase when a buffer full condition prevents the continued transfer of data from the media to the data buffer. The
buffer under run counter is incremented during operations that require a Data Out phase when a buffer empty condition pre-
vents the start or continuation of a data transfer from the data buffer to the media (or a data transfer from the media for a Verify
command with BytChk=1).
Buffer Overrun conditions are detected during the following SCSI commands:
• READ (6)
• READ (10)
Buffer Under Run conditions are detected during the following SCSI commands:
• VERIFY WITH BytChk=1
• VERIFY (16) WITH BytChk=1
• WRITE (6)
• WRITE (10)
• WRITE AND VERIFY
• WRITE AND VERIFY (16)
• WRITE SAME
• WRITE SAME (16)
• ZERO SEEKS
The number of times no seek was required. The operation may have resulted in a head switch.
• SEEKS >= 2/3 DISK
The number of seeks equal to or greater than 2/3 of the disk.
• SEEKS >= 1/3 AND < 2/3 DISK
The number of seeks equal to or greater than 1/3 and less than 2/3 of the disk.
• SEEKS >= 1/6 AND < 1/3 DISK
The number of seeks equal to or greater than 1/6 and less than 1/3 of the disk.
• SEEKS >= 1/12 AND < 1/6 DISK
The number of seeks equal to or greater than 1/12 and less than 1/6 of the disk.
• SEEKS > 0 AND < 1/12 DISK
The number of seeks less than 1/12 of the disk.
• OVERRUN COUNTER
The number of times that data was available to be transferred from the media but the device buffer still contained data
that had not been retrieved by the Initiator. Consequently, the disk had to take additional revolutions until the buffer
was available to accept data.
• UNDER RUN COUNTER