Case:The customer’s hard disk has only one logical partition, and the customer finds the data loss after cutting the data for one month. Solution:For cutting data in the cutting data area, the key is that the hard disk has only one logical partition. The system will generate a large number of temporary files. The number…
Case:Customer desktop computer hard disk access cannot be recognized, and the hard disk has no response. Solution:After testing, the hard disk circuit board was burned, and now I am worried that the magnetic head has been burned out, so I found a circuit board of the same type for heat exchange to test whether there…
We first look at the following two pictures. Picture 1 is the “BIOS CHIP” of the circuit board. When we replace the PCB, we need to swap the “BIOS CHIP” with your original PCB. Picture 2 shows the “Board Number” of the board, and the “Board Number” must be the same! FAQs of BF41-00281A PCB…
Disabling Auto-Relocation and SMART Attribute Processing
While the methods outlined in the previous section go a long way to obtaining an image of the data, other problems remain.
When drive firmware identifies a bad sector, it may remap the sector to a reserved area on the disk that is hidden from the user (Figure 3). This remapping is recorded in the drive defects table (G-list). Since the bad sector could not be read, the data residing in the substitute sector in the reserved area is not the original data. It might be null data or some other data in accordance with the vendor-specific firmware policy, or even previously remapped data in the case where the G-list was modified due to corruption.
Moreover, system software is unaware of the remapping process. When the drive is asked to retrieve data from a sector identified as bad, the drive firmware may automatically redirect the request to the alternate sector in the reserved area, without notifying the system before the error is returned. This redirection occurs despite the fact that the bad sector is likely still readable and only contains a small number of bytes with errors.
Figure 3: G-List Remapping
This process performed by drive firmware is known as bad sector auto-relocation. This process can and should be turned off before the imaging process begins. Auto-relocation on a drive with read instability not only obscures instances when non-original data is being read, it is also time-consuming and increases drive wear, possibly leading to increased read instability.
Effective imaging software should be able to turn off auto-relocation so that it can identify problem sectors for itself and take appropriate action, which ensures that the original data is being read.
Unfortunately, the ATA specification does not have a command to turn off auto-relocation. Therefore imaging software should use vendor-specific ATA commands to do this.
A similar problem exists with Self-Monitoring Analysis and Reporting Technology (SMART) attributes. The drive firmware constantly recalculates SMART attributes and this processing creates a large amount of overhead that increases imaging time and the possibility of further drive degradation. Imaging software should be able to disable SMART attribute processing.
Other drive preconfiguration issues exist, but auto-relocation and SMART attributes are among the most important that imaging software should address.
Increasing Transfer Speed with UDMA Mode
Modern computers are equipped with drives and ATA controllers that are capable of the Ultra Direct Memory Access (UDMA) mode of data transfer. With Direct Memory Access (DMA), the processor is freed from the task of data transfers to and from memory. UDMA can be thought of as an advanced DMA mode, and is defined as data transfer occurring on both the rise and fall of the clock pulse, thus doubling the transfer speed compared to ordinary DMA.
Both DMA and UDMA modes are in contrast to the earlier Programmed Input Output (PIO) mode in which the processor must perform the data transfer itself. Faster UDMA modes also require an 80-pin connector, instead of the 40-pin connector required for slower UDMA and DMA.
The advantages are obvious. Not only does UDMA speed up data transfer, but the processor is free to perform other tasks.
While modern system software is capable of using UDMA, imaging software should be able to use this data transfer mode on a hardware-level (bypassing system software) as well. If the source and destination drives are on separate IDE channels, read and write transfers can occur simultaneously, doubling the speed of the imaging process. Also, with the computer processor free, imaged data can be processed on the fly. These two advantages can only be achieved if the imaging software handles DMA/UDMA modes, bypassing system software. Most imaging tools currently available on the market use system software to access the drive and so don’t have these advantages.
Microsoft’s FAT32 File System
Windows 95 OSR2 provides an updated version of the File Allocation Table file system called FAT32. This updated file system allows for a default cluster size as small as 4K, as well as support for EIDE hard disc sizes in excess of 2 Gbytes. FAT32 provides many enhancements over previous implementations of the FAT file system.
Cluster & Partition Sizes
FAT32 supports drives up to 2 terabytes in size. FAT32 uses smaller clusters (that is, 4K clusters for drives up to 8 Gbytes in size), resulting in 10 to15 percent more efficient use of disc space relative to large FAT16 partitions. FAT32 will only work on 512 Mbytes and larger drives. Microsoft’s bundled disc tools (Format, FDISK, Defrag, and MS-DOS based ScanDisk) have been revised to work with FAT32.
Note: Please backup all data.
1. QUESTION
When I try to format a FAT32 file system partition larger than 8025 Mbytes from within Windows 95, I receive the following error:Verifying xxx.xx M
Invalid media or track 0 bad-disk unusable
Format terminated
REASON
This error occurs if there is a non-DOS partition preceding the extended DOS partition and the primary DOS partition has been formatted using the real-mode FORMAT.EXE command.
SOLUTION
2. QUESTION
When I try to partition a drive that is larger than 8 Gbytes in size, the maximum partition size is still 8 Gbytes.
REASON
This can occur if the hard disc controller does not fully support the interrupt 13 extensions. In order for a hard disc that is both larger than 8 Gbytes and using the FAT32 file system to be fully addressed, it must support interrupt 13 extensions. The file IO.SYS tests for the presence of interrupt 13 extensions, and if they are not found, uses the default CHS LBA limit of 7.9 Gbytes. This information applies to both ATA and SCSI hard disc drives.
SOLUTION
Contact the drive controller’s manufacturer for information about a possible BIOS upgrade to a version of the BIOS that fully supports interrupt 13 extensions.
3. QUESTION
When I check in FDISK to see if my partition is FAT32, it only shows FAT16. How do I get my drive to be partitioned in FAT32?
REASON
SOLUTION
Run the FDISK tool which came with OSR2 on a system with a drive over 512 Mbytes. FDISK will ask whether you wish to enable large disc support. If you answer Yes, any partition you create larger than 512 Mbytes is marked as a FAT32 partition.
4. QUESTION
When I try to dual-boot Windows version 3.x on a computer running Windows OSR2, I receive one of the following error messages:
- This version of Windows does not run on MS-DOS 6.x or earlier.
- You started your computer with a version of MS-DOS incompatible with this version of Windows. Insert a Startup diskette matching this version of Windows and then restart.
- The system has been halted. Press CTRL+ALT+DELETE to restart your computer.
- This version of Windows cannot be run on this version of DOS.
REASON
Starting with OSR2, dual-booting Windows 3.x is not supported in Windows 95.
SOLUTION
To dual-boot between Windows 3.x and Windows 95, install the retail version of Windows 95. If you have FAT32 partitions, remove them and create a FAT16 partition with the Windows 95 or MS-DOS 6.x version of FDISK.EXE.
Neither MS-DOS 6.x nor the retail version of Windows 95 will recognize a FAT32 volume. Windows 3.x was designed to use the FAT12 and FAT16 file systems. It could potentially damage a FAT32 volume.
5. QUESTION
When I try to compress my drive with DriveSpace or DriveSpace 3, I get the following error:Drive C cannot be compressed because it is a FAT32 drive.
REASON
DriveSpace was designed to work with the FAT12 and FAT16 file systems and cannot be used with drives using the FAT32 file system.
SOLUTION
None at this time.
6. QUESTION
When I try to defragment a FAT32 partition, I receive the following error:Windows cannot defragment this drive. Make sure the disk is formatted and free of errors. Then try defragmenting the drive again.
REASON
This can be caused by running an earlier version of DEFRAG.EXE than the version included with OSR2.
SOLUTION
Extract a new copy of the DEFRAG.EXE file from your original OSR2 CD-ROM or discs. For additional information about how to extract or obtain the OSR2 version of DEFRAG.EXE, contact you OEM vendor or Microsoft technical support.
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