Troubleshooting of hard drive data

In order to effectively save the data in the hard disk, in addition to regular backup work, we also need to learn how to save the hard disk when the hard disk fails, or extract useful data from the bad area, minimize the loss.

Hard Disk not recognized by System

The system cannot be started from the hard disk, nor can it be started from disk A into disk C. The existence of the hard disk cannot be found by using the automatic monitoring function in CMOS. Most of these failures occur on the connection cable or IDE port. The failure of the hard disk itself is unlikely. You can re-plug the hard disk cable or change the IDE port and cable to conduct replacement tests, you will soon find the fault. If the new hard disk is not accepted, a common cause is the master-slave jumper on the hard disk. If an IDE hard disk is connected to two hard disk devices online, the master-slave relationship should be clearly defined.

Fault Caused by CMOS

Whether the hard disk type in CMOS is correct directly affects the normal use of the hard disk. Currently, all machines support the "IDE Auto Detect" function to automatically Detect the hard disk type. When the hard disk type is wrong, sometimes the system cannot be started, sometimes the system can be started, but a read/write error occurs. For example, if the hard disk type in CMOS is smaller than the actual hard disk capacity, the sectors behind the hard disk cannot be read or written. If the disk type is multi-partition, individual partitions will be lost. There is another important cause of failure. Because the current IDE supports the Logic Parameter type, the hard disk can adopt "Normal, LBA, Large" and so on. If data is installed in Normal mode, changing to another mode in CMOS will cause a read/write error on the hard disk. Because the ing relationship has changed, the original hard disk location cannot be read.

Startup Fault Caused by the Main Boot Program

The primary boot program is located in the primary Boot Sector of the hard disk. It is mainly used to check the correctness of the hard disk partition, determine the active partition, and hand over the boot right to the DOS or other operating systems of the active partition. If the program is damaged, it cannot be booted from the hard disk, but the hard disk can be read and written after being started from the soft drive or optical drive. The solution to this fault is relatively simple. It is most convenient to use the FDISK of the higher DOS version. When the FDISK with parameters/mbr is running, the primary boot program of the hard disk will be directly replaced (overwritten. In fact, the Main Boot Sector of the hard disk is created by this program. FDISK. EXE contains the complete Main Boot Program of the hard disk. Although the DOS version is constantly updated, the Main Boot Program of the hard disk has not changed, from DOS 3. for DOS from x to ipvs 98, you only need to find a DOS boot disk to start the system and run this program to fix it.

Startup Fault Caused by Partition Table Error

Partition Table errors are serious hard disk errors. Different levels of errors may cause different losses. If there is no active partition flag, the computer cannot start. However, you can read and write the hard disk after the drive or the Drive boot system. You can use FDISK to reset the active partition for repair.

If a partition type is incorrect, the loss of a partition may occur. The fourth byte of the partition table is the partition type value. Normally, the basic DOS partition value larger than 32 MB is 06, and the extended DOS partition value is 05. Many people use this type of value to encrypt a single partition and restore the original correct type value to restore the partition to normal.

The partition table contains other data used to record the start or end address of the partition. Damage to the data will cause confusion or loss of the partition. The available method is to re-write the data in the backup partition table, you can also obtain partition table data from other hard disks of the same type and with the same partition status.

The recovery tool can use tools such as NU for easy operation. Of course, you can also use DEBUG for operations, but the operations are cumbersome and risky.

Partition valid flag error fault

There is also an important part in the Main Boot Sector of the hard disk, that is, the last two bytes: "55aa", which is a valid symbol of the sector. When the disk is started from a hard disk, floppy disk, or disc, the two bytes are detected. If the disk exists, the hard disk exists. Otherwise, the hard disk is not recognized. This can be used for the encryption technology of the entire hard disk, and the DEBUG method can be used for recovery. In addition, when the DOS boot sector does not have a boot flag, the System starts to display "Mmissing Operating System ". The convenient method is to use the following common repair methods for the dossystem.

Startup Fault Caused by DOS boot System

The DOS boot system consists of the DOS Boot Sector and the DOS system file. System files mainly include IO. SYS, MSDOS. SYS, COMMAND. COM, where COMMAND. COM is a DOS shell file, which can be replaced by other similar files, but is a required file for DOS Startup by default. In Windows 98, MSDOS. SYS is a text file that is required to start Windows. This file is not used only when DOS is started. When a DOS boot error occurs, you can boot the system from a floppy disk or a CD and use the sys c: Command to transfer the system to fix the fault, including the Boot Sector and system files.

Read/write failures caused by FAT tables

The FAT table records the storage address of the hard disk data. Each file has a set of FAT chains to specify the address of the cluster to store. Corruption of the FAT table means the loss of file content. Fortunately, the DOS system provides two FAT tables. If the current FAT table is damaged, the second FAT table can be replaced. However, because the length of the FAT table of disks of different specifications and the address of the second FAT table are not fixed, you must find the correct position in the fix, some tool software such as NU has such repair functions and is very convenient to use. DEBUG can also be used to achieve this operation, that is, use its m command to move the second FAT table to the first table. If the second FAT table is damaged, the hard disk cannot be restored to its original state, but the file data is still stored in the data area of the hard disk, you can use the CHKDSK or SCANDISK command to fix the issue *. CHK file, which is the loss of the sector data of the FAT chain. If it is a text file, you can extract the complete or part of the file content from it.

Guide Fault Caused by directory Table Corruption

The directory table records the file name and other data in the hard disk. The most important one is the starting cluster number of the file. Because the directory table does not have the automatic backup function, a large number of files will be lost if the directory is damaged. One way to reduce the loss is to use the CHKDSK or SCANDISK program to restore the method, search for * from the hard disk *. CHK file, because the directory table is damaged, only the first cluster number is lost, each *. the CHK file is a complete file. Change it to the original name to restore most files.

Data Recovery during accidental deletion of partitions

After the hard disk partition is deleted using FDISK, the data on the hard disk disappears completely. When the hard disk is not formatted, it is displayed as an invalid drive. If you understand how FDISK works, you will know that FDISK only rewrites the content in the primary Boot Sector of the hard disk (0-sided 0-Sector 1-sector). Specifically, it deletes the partition table information of the hard disk, the data in any partition on the hard disk has not changed. You can recover the original partition and data by following the preceding solution to partition table errors. If you have already formatted the partition, you can restore the partition data in the following way after the partition is restored.

Recover accidentally formatted Hard Disk Data

In a high version of DOS, the FORMAT formatting operation creates disk information for restoring formatting by default, in fact, the DOS Boot Sector, FAT partition table, and directory table of the disk are copied to the last several sectors of the disk (because the following sectors are rarely used ), the content in the Data zone has not changed at all. In this way, you can run the UNFORMAT command to restore it. In addition, DOS also provides a MIROR command to record the information of the current disk for formatting or restoration after deletion. This method is also effective.