Ten great tricks to rescue hard drive failure

A large amount of useful data is stored in the hard disk of each user, and the hard disk is a vulnerable part. In order to effectively save the data in the hard disk, in addition to effectively saving the data in the hard disk and backing up, you must also learn how to rescue the hard disk when the hard disk fails, or extract the useful data to minimize the loss.

1. The system does not recognize the hard disk

Such failures are more common, that is, they cannot be started from the hard disk, and cannot be accessed from the A disk to enter the C disk. The automatic monitoring function in CMOS can not be used to detect the existence of the hard disk. Most of these faults appear on the connecting cable or IDE port. The failure rate of the hard disk itself is very small. You can replace the hard disk cable or replace the IDE port and cable for replacement test. You can quickly find the fault. If the newly connected hard disk does not recognize, there is another common reason is the master-slave line on the hard disk. If the hard disk is connected to the IDE master disk position, the hard disk must be jumped to the master disk shape. Jumper errors are generally not detected. hard disk.

2. Failure caused by CMOS

The correctness of CMOS directly affects the normal use of the hard disk, here mainly refers to the type of hard disk. Fortunately, all current machines support the "IDE auto detect" function, which can automatically detect the type of hard disk. When connecting a new hard disk or replacing a new hard disk, you must re-set the type through this function. Of course, some types of motherboards can automatically recognize the type of hard drive. When the hard disk type is wrong, sometimes the system cannot be started at all, sometimes it can be started, but read and write errors will occur. For example, the type of hard disk in CMOS is smaller than the actual hard disk capacity, the sectors behind the hard disk will not be readable and writable. If it is in a multi-partition state, individual partitions will be lost. There is also an important cause of failure. Since the current IDE supports logical parameter types, the hard disk can be Normal, LBA, Large, etc. If the data is installed in the general mode, and the CMOS is changed to another mode, a read and write error of the hard disk will occur, because the mapping relationship between its physical geology has changed and the original correct hard disk position cannot be read. .

3. The startup failure caused by the main boot program

The main boot sector of the hard disk is the most sensitive part of the hard disk. The main boot program is part of it. This program is mainly used to detect the correctness of the hard disk partition and determine the active partition. It is responsible for handing over the right to boot DOS or other operating systems for active partitions. If this part of the program is damaged, you will not be able to boot from the hard disk, but you can read and write to the hard disk from the soft or optical area. The method to fix this fault is relatively simple. It is most convenient to use fdisk of the higher version DOS. When running with the parameter / mbr, the main boot program of the hard disk will be directly replaced (rewritten). In fact, the main boot sector of the hard disk is created by this program, fdisk. Exe contains the complete hard disk master boot program. Although the DOS version is constantly updated, the main boot program of the hard disk has not changed from DOS 3. x To the DOS that currently has winDOS 95, so as long as you find a DOS boot disk to start the system and run this program, you can repair it. In addition, other tool software such as kv300 also has this function.

4. The startup failure of the partition table error boot

Partition table errors are serious errors of the hard disk, and different degrees of errors will cause different losses. If there is no active partition flag, the computer cannot start. However, after booting the system from the soft zone or optical zone, the hard disk can be read and written, and the active partition can be reset by fdisk to repair. If the type of a certain partition is wrong, it may cause the loss of a certain partition. The fourth byte of the partition table is the partition type value, the normal bootable basic DOS partition value greater than 32mb is 06, and the extended DOS partition value is 05. If the basic DOS partition type is changed to 05, the system cannot be started, and the data in it cannot be read or written. If you change 06 to a type that DOS does not recognize, such as efh, DOS thinks that changing the partition is not a DOS partition, and of course cannot read and write. Many people use this type of value to implement the encryption technology of a single partition, and restore the original correct type value to restore the partition to normal. There are other data in the partition table for recording the start or end address of the partition. The damage of these data will cause chaos or loss of the partition. Generally, manual recovery is impossible. The only way is to use the backup partition table data to write back, or obtain the partition table from other hard disks of the same type and the same partition status Data, otherwise it will cause permanent loss of other data. When operating on the main boot sector, tools such as nu can be used. The operation is very convenient, and the main boot sector of the hard disk can be directly read, written or edited. Of course, debug can also be used for operation, but the operation is cumbersome and has certain risks.

5. Hard disk failure caused by wrong partition effective sign

There is also an important part in the main boot sector of the hard disk, that is its last two bytes: 55aah, this word is a valid sign of the sector. When booting from a hard disk, floppy disk, or optical zone, these two bytes will be detected, and if it exists, it is considered that there is a hard disk, otherwise the hard disk will not be recognized. When this logo is started from the hard disk, it will be transferred to rom basic or prompted to put in the floppy disk. Cannot transfer to hard disk when booting from floppy disk. Here can be used for the encryption technology of the entire hard disk. The debug method can be used for recovery processing. In addition, the DOS boot sector still has such a logo. When the DOS boot sector has no boot logo, the system startup will display as: "missing operating system". The repair method can use the main boot sector repair method, but the address is different, the more convenient method is to use the following general DOS system repair method.

6. Startup failure caused by DOS boot system

DOS boot system is mainly composed of DOS boot sector and DOS system files. The system files mainly include iosys, msdos.sys, command.com, where command.com is a DOS shell file, which can be replaced with other similar files, but by default it is a necessary file for DOS startup. In the DOS system carried by Windows 95, msdos.sys is a text file and is a necessary file to start Windows. However, this file is not needed when starting DOS only. However, when the DOS boot fails, the system can be booted from a floppy disk or a CD, and then the system can be repaired using sys c: transfer system, including the boot sector and system files can be automatically repaired to a normal state.

7. Read and write failure caused by FAT table

The fat table records the storage address of the hard disk data, and each file has a set of connected fat chains to specify the cluster address where it is stored. The corruption of the fat table means the loss of file content. Fortunately, the DOS system itself provides two fat tables. If the currently used fat table is damaged, you can use the second one to overwrite and repair it. However, because the length of the fat table and the address of the second fat table of the disks with different specifications are also not fixed, it is necessary to correctly find the correct location when repairing. Some tool software such as nu etc. has such a repair function. Very convenient. This operation can also be achieved by using debug, that is, using its m command to move the second fat table to the first table. If the second fat table is also damaged, the hard disk cannot be restored to its original state, but the data of the file is still stored in the data area of ​​the hard disk. You can use the chkdsk or scandisk command to repair it, and finally get *. chk file, this is the sector data of the lost fat chain. If it is a text file, it can be extracted from it and the complete file can be merged. If it is a binary data file, it is difficult to recover the complete file.

8. Boot failure caused by damage to the catalog table

The directory table records data such as the file name of the file in the hard disk. The most important item is the starting cluster number of the file. Since the directory table does not have an automatic backup function, a large number of files will be lost if the directory is damaged. One way to reduce losses is to use the above chkdsk or scandisk program to search for chk files from the hard disk. When the directory table is damaged, the first cluster number is lost. The chk files formed when fat is damaged are generally all Comparing complete file data, each chk file is a complete file, and changing it to the original name can restore most files.

9. Data recovery when accidentally deleting partitions

After deleting the hard disk partition with fdisk, the surface phenomenon is that the data in the hard disk has completely disappeared, and the invalid drive will be displayed when entering the hard disk when it is not formatted. If you understand the working principle of fdisk, you will know that fdisk just rewritten the contents of the hard disk's main boot sector (0 side 0 track 1 sector). Specifically, the partition table information of the hard disk is deleted, and the data of any partition in the hard disk has not changed. The above method for repairing the partition table error can be imitated. This is limited to after removing or rebuilding the partition. If the partition has been formatted with format, after restoring the partition first, restore the partition data as follows.

10. Recovery of data from accidentally formatted hard disk

In the DOS high version state, the format operation format has been established by default to restore the formatted disk information. In fact, all the contents of the disk DOS boot sector, fat partition table and directory table are copied to In the last few sectors of the disk (because the following sectors are rarely used), the contents of the data area have not changed at all. In this way, you can restore the original file allocation table and directory table by running "unformat c:" to complete the recovery of hard disk information. In addition, DOS also provides a mirror command to record the current disk information for recovery after formatting or deleting. This method is also more effective.