Sun Microsystems StorageTek T9840, Руководство пользователя

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Mixed Media Management
36 T9840 User’s Reference Manual • September 2008 Revision YA • 95739
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If a T9840A/B drive has down level drive firmware, a high-density data cartridge
would be considered as a blank tape cartridge; and, a low-density data cartridge
would lose statistical data stored in the FIB during a previous mount into a
T9840C drive.
Exceptional MIR Processing
There are instances when the MIR process departs from the normal.
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Write Protect
When the tape cartridge is write protected, neither the MIR nor FIB is rewritten and
statistical information for that mount is not captured. If the tape cartridge is in a
library that logically write protects the tape cartridge, the MIR is updated as normal
on each dismount.
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Major Error/Power Off
If a tape cartridge is mounted and the drive SNO's (should not occur error) or loses
power, the drive memory-resident MIR is not written to the tape media. Instead after
IPL (initial program load), the drive will read the existing MIR on tape. Special data
is saved in EEPROM that will allow the existing MIR to be updated and rewritten to
the media with the valid flag set. Therefore, the MIR will contain all positioning
information up to the last mount and this tape will operate with mixed performance
until EOD is found. T9840A/B/C drives must have the appropriate drive firmware
level to update the MIR after a SNO or power loss, see
“Mixed Media Management”
on page 31 .
Invalid MIR Correction
Once a tape cartridge has an invalid MIR, some action is required to correct it. An
invalid MIR can be corrected in several ways using the drive model that created the
cartridge (for example: a T9840A/B formatted cartridge in a T9840A/B drive or a
T9840C formatted cartridge in a T9840C drive).
1. Reading to the end of existing data (EOD) creates a complete and valid MIR. This is
done at normal read speeds and could take up to 45 minutes, for a full 9840 tape
cartridge.
2. Appending to the tape cartridge will also create a valid MIR, although a slow speed
read must first be done to the end of existing user data.
3. The Drive Operation Menu (offline) “Rebuild MIR” utility will sequentially read
from block ID 0 to the EOD. The MIR will be complete and valid when the tape
cartridge is unloaded (see
“Build MIR” on page 77 ).
4. The Drive Operation Menu (offline) “Make Data Tape” utility will reformat the tape
cartridge with a valid MIR. However, all previous data will be lost (see “Reformat a
Cartridge” on page 76 ).
The memory-resident MIR is always rebuilt to the last block read, on-the-fly, during
normal read/write functions. When the partially rebuilt memory-resident MIR is
written to the tape during the download process, the invalid flag is reset because the
MIR is now partially valid. This can result in seemingly conflicting performance from a
single tape.