Product manual

Spinpoint M9TU-USB 3.0 Product Manual REV 1.0
22
DISK DRIVE OPERATION
• INITIALIZE DEVICE PARAMETER (91h)
• SLEEP (99h, E6h)
• STANDBY IMMEDIATELY (94h, E0h)
• READ BUFFER (E4h)
• WRITE BUFFER (E8h)
• WRITE SAME (E9h)
5.5.2 Write Caching
Write caching improves both single and multi-sector write performance by reducing delays introduced by
rotational latency. When the drive writes a pattern of multiple sequential data, it stores the data to a cache
buffer and immediately sends a COMMAND COMPLETE message to the host before it writes the data to the
disk.
The data is then written collectively to the drive thereby minimizing the disk seeking operation. Data is
held in cache no longer than the maximum seek time plus rotational latency. Host retries must be enabled
for Write Caching to be active.
If the data request is random, the data of the previous command is written to the disk before COMMAND
COMPLETE is posted for the current command. Read commands work similarly. The previous write is
allowed to finish before the read operation starts.
If a defective sector is found during a write, the sector is automatically relocated before the write occurs.
This ensures that cached data that already has been reported as written successfully gets written, even if an
error should occur.
If the sector is not automatically relocated, the drive drops out of write caching and reports the error as an ID
Not Found. If the write command is still active on the AT interface, the error is reported during that
command. Otherwise, it is reported on the next command.
5.5.3 Defect Management
The Spinpoint M9TU-USB 3.0 hard disk drive media is scanned for defects. After defect scanning, the
defective sectors are saved in the defect list. A defect encountered in the manufacturing process is slipped to
the next physical sector location. All logical sector numbers are pushed down to maintain a sequential order
of data. The read/write operation can “slip” over the defective sectors so that the only performance impact is
idle time.
5.5.4 Automatic Defect Allocation
The automatic defect allocation feature automatically maps out defective sectors encountered during read
sector or write sector operations. These types of defective sectors are typically caused by grown defects.
During write operations, if write errors are encountered, all sectors within the target servo frame are mapped
out. Original data is transferred and written into designated reserved sector areas determined by the HDD
firmware.
5.5.5 Multi Parities Error Correction
The drive uses LDPC code with parity to perform error detection and correction. For each 4K bytes
block, the software error correction polynomial is capable of correcting:
• 320-bit burst error
These errors are corrected on the fly with no performance degradation.