Quantum LTO 4, Руководство пользователя

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SCSI Commands: 50BVERIFY Page 215
3.38 VERIFY
The VERIFY command verifies one or more blocks of data beginning with the next
block from the tape unit.
The command terminates after the specified number of bytes or blocks are verified
or when the drive encounters a filemark, the EOD, the EOM, or an unrecoverable
error. On completion the medium is positioned after the last block verified, after the
end-of-data, after a filemark or after an unrecoverable block.
If a VERIFY with a zero verification length is issued, no data is verified, and the
current position on the tape does not change. This condition is not considered an
error.
The VERIFY command causes data to be read from the tape and passed through
the drive’s error detection and correction hardware to determine whether it can be
recovered from the tape. The amount of data to be read is indicated by the
Verification Length field and the Fixed bit in the same manner as is used in a READ
command.
3.38.1 VERIFY Command Descriptor Block
Byte Bits
7 6 5 4 3 2 1 0
0 Operation Code (13h)
1 Ignored LUN Reserved Fixed
2 (MSB)
3
4
Verification Length
(LSB)
5 Control
3.38.1.1 VERIFY Command Field Descriptions
Field Bytes Bits Description
Operation
Code 0 The Operation Code for VERIFY is 00h.
Ignored
Logical
Unit 1 5-7 The LUN field is vestigial from the SCSI-1 standard and is ignored.
Fixed 1 0 0 = Variable block length. Verify Length contains the number of
bytes to return.
1 = Fixed block length, as specified by the MODE SELECT Block
Descriptor. Verify Length contains the number of blocks to
return
Verify
Length 2-4 This field specifies the number of bytes (Fixed = 0) or blocks (Fixed
= 1) to be verified. A verification length of 0 is valid and no data is
verified.
Reserved All reserved bits must be 0.
Control 5 See SCSI Command Control Byte Format on page 25.