Sun Microsystems StorageTek T9840, Руководство пользователя

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Mixed Media Management
95739 • Revision YA Chapter 1 Overview 33
Normal MIR Processing
Every time a tape cartridge is loaded, the MIR is read from the tape media and saved in
the drive memory. When the MIR is loaded in drive memory, an invalid flag is written
in the tape-resident MIR. The tape-resident MIR is marked invalid because it does not
reflect results of activity in the current mount session. All subsequent MIR accesses
during the current mount session are saved in the memory-resident MIR.
When the tape cartridge is unloaded, as part of the unload routine, the memory-
resident MIR information is written to the tape-resident MIR and the MIR invalid flag
is turned off. A copy of the memory-resident MIR is stored in the drive’s persistent
memory (EEPROM) and used should the MIR fail to be written because of a power
failure or firmware problem (SNO or should not occur).
Cross-Density MIR Processing
Whenever a data cartridge is loaded that was written in a data density format that is
different from the one used when the drive writes, model-specific MIR processing
occurs. The following explanations cover:
■
T9840D tape drive loaded with a lower-density cartridge
■
T9840C tape drive loaded with aT9840D-written data cartridge
■
T9840C tape drive loaded with a T9840A/B-written data cartridge
■
T9840A/B drive loaded with a high-density tape cartridge
T9840D Tape Drive Loaded With a Lower-Density Cartridge
When the T9840D drive detects that a data cartridge is loaded, the drive first looks in
the designated location for a T9840D MIR. If a T9840D MIR is not found, the drive then
checks for a T9840C MIR and, if its not found, it then checks for a T9840A/B MIR. The
processing for these operations is described in the sections below. If the MIR cannot be
read, the T9840D drive attempts to recover its contents using any portions of the MIR
that can be read and the contents of the Format Identity Burst (FIB).
Note – The FIB is written in a format that can be read by T9840C and T9840A/B drives
if they have an appropriate level of firmware.
The T9840D uses a memory-resident copy of the MIR to access user data pointers for
read-only functions. Statistical counters are continuously updated in the memory-
resident MIR with any drive activity.
When the data cartridge is unloaded, the T9840D drives writes the FIB to the high-
density MIR location.
Notes:
■
When the T9840D drive identifies the data cartridge as a low-density data format,
i.e., written by a T9840C or T9840A/B, it displays
Ready L
on its operator panel.
■
The T9840D tape drive cannot correct or cause an invalid MIR on a T9840C
written data cartridge. A T9840C MIR can only become invalid during a mount on
a T9840C drive.