10 tips for troubleshooting hard drives

Each user's hard drive is stocked with a lot of useful data, and the hard drive is an easy-to-use component. In order to effectively save the data on the hard disk, in addition to the effective storage of data on the hard disk, backup work, but also learn how to save the hard drive in the event of failure, or extract the useful data, minimize the loss .

1. The system does not recognize the hard drive

This kind of fault is more common, that is, from the hard drive can not start, from a disk boot also cannot enter the C drive, using the automatic monitoring function in CMOS can not find the existence of the hard disk. Most of this fault occurs on the connection cable or IDE port, the hard disk itself has very little failure rate. Replacement tests can be performed by reseating the hard drive cable or by changing the IDE port and cable, which can quickly identify the fault. If the new drive is not recognized, there is also a common reason is the master and slave on the hard disk, if the hard disk is connected to the IDE's main disk location, the hard disk must jump to the primary disk, Jumper errors generally cannot detect a hard drive.

2.cmos caused by the fault

CMOS correct or not directly affect the normal use of the hard drive, here refers to the hard disk type. Fortunately, the current machine supports the "IDE Auto Detect" feature, which automatically detects the type of hard disk. This feature is used to reset the type of the drive when a new hard disk is connected or replaced. Of course, There are now types of motherboards that automatically recognize the type of hard disk. When the hard disk type is wrong, sometimes it is impossible to start the system at all, and sometimes it can be started, but read and write errors occur. For example, the hard disk type in CMOS is less than the actual hard disk capacity, then the sector behind the hard drive cannot read and write. If it is multi-partition state, individual partitions will be lost. There is also an important cause of failure, because the current IDE supports logical parameter types, hard disk can be used Normal,lba, large and so on. If the data is installed in the normal mode, and the other mode is changed in CMOS, A hard disk read-write error occurs because its physical geology mapping has changed and will not be able to read the original correct hard disk location.

3. Startup failure caused by the master boot program

The main boot sector of the hard disk is the most sensitive part of the hard disk, the main boot is part of it, this program is mainly used to detect the correctness of the partition of the hard disk, and determine the active partition, is responsible for the transfer of the boot to the active partition DOS or other operating system. This program is corrupted and will not boot from the hard disk However, the hard drive can be read and written from the soft or light area. The easiest way to fix this failure is to use FDISK with a high version of DOS, which will replace (rewrite) The main boot of the hard drive directly when the parameter/mbr is running. Actually, the main boot sector of the hard drive is created by this program, The Fdisk.exe contains a complete hard drive master boot program. Although the DOS version is constantly updated, but the main boot program of the hard disk has not changed, from DOS 3.x to the current WinDOS 95 dos, so just find a DOS boot disk boot system and run this program can be repaired. In addition, Other tool software such as kv300 also has this feature.

4. partition table error booting boot failure

Partition Table error is a hard disk serious error, the degree of different errors will cause different losses. If there is no active partition flag, the computer cannot start. However, after booting the system from a soft or light area, you can read and write to the hard disk, and you can reset the active partition by using Fdisk to fix it. If it is a partition type error, Can cause a partition to be lost. The fourth byte of the partitioned table is the partition type value, and the normal bootable base DOS partition value greater than 32MB is 06, while the Extended DOS partition value is 05. If you change the base DOS partition type to 05, you cannot start the system. and cannot read and write the data. If you change the 06 to DOS unrecognized type such as EFH, then DOS think partition is not DOS partition, of course, can not read and write. Many people use this type of value to implement a single partition of the encryption technology, Restoring the original correct type value will restore the partition to normal. Other data in the partition table is used to record the starting or ending address of the partition. The damage to this data can cause confusion or loss of the partition, and it is generally not possible to manually recover, the only way is to re-write back with the backup partition table data. or get partition table data from other hard disks of the same type and partition status, otherwise the data will be permanently lost. In the operation of the main boot sector, the NU and other tools can be used, the operation is very convenient, You can read or write directly to the main boot sector of the hard drive. Of course, you can also use debug, but the operation is cumbersome and has a certain risk.

5. Hard disk failure due to partition valid flag error

There is also an important part of the hard drive main boot sector, which is its last two bytes: 55aah, which is a valid flag for the sector. When booting from a hard disk, a floppy disk or a light area, this two bytes will be detected and the hard drive will not be recognized if there is a hard disk present. This flag when booting from hard disk will be transferred Basic or prompt to insert a floppy disk. cannot be transferred to the hard disk when booting from a floppy disk. This can be used for encryption of the entire hard drive. The Debug method is used to restore processing. In addition, the DOS boot sector still has such a flag, when the DOS boot sector does not have a boot flag, the system boot will be displayed as: "Missing Operating system ". Its method of repair can be used in the main boot sector repair method, but the address is different, the more convenient way is to use the following DOS system common repair method.

Boot failure due to 6.dos boot system

DOS boot system mainly consists of DOS boot sector and DOS system files. system files mainly include Io.sys, msdos.sys,command.com, wherein Command.com is a DOS shell file, can be replaced by other similar files, However, the default is the DOS boot required files. Msdos.sys is a text file that is required to start Windows in a DOS system that is carried by Windows 95. But this file is not available when booting DOS only. However, when DOS boot error occurs, you can boot the system from a floppy disk or a CD-ROM. The SYS c: Transfer system can then be used to repair the fault, including boot sector and system files can be automatically repaired to normal state.

Read and write failures caused by 7.fat tables

The Fat table records the storage address of the hard disk data, and each file has a set of connected fat chains that specify the address of the cluster to which it resides. Corruption of fat table means the loss of the contents of the file. Fortunately, the DOS system itself provides two fat tables, if the FAT table currently used is damaged, You can use the second overwrite fix. However, because the size of the fat table and the address of the second fat table are not fixed because of the different specifications of the disk, the repair must correctly find its correct location, by some tool software such as the NU itself has such a repair function, Use is also very convenient. This can also be done using debug, which uses its m command to move the second fat table to the first table. If the second Fat table is also damaged, you cannot restore the hard drive to its original state, but the file data is still stored in the data area of the hard disk. It can be repaired with the Chkdsk or ScanDisk command, resulting in the *.chk file, which is the loss of the fat chain's sector data. If it is a text file you can extract and merge the complete file, if it is a binary data file, it is difficult to recover the full file.

8. Boot failure due to damage to catalog table

The directory table records data such as file names on the hard disk, the most important of which is the starting cluster number of the file, the directory table because there is no automatic backup function, so if the directory corruption will be lost a large number of files. One way to reduce losses is to use the above Chkdsk or ScanDisk program, The Chk file from the hard disk search, by the Catalog table corruption is the first cluster number is lost, in the case of fat is damaged in the formation of the Chk file is generally more complete file data, each CHK file is a complete file, it is changed to the original name can restore most files.

9. Recovery of data when deleting partitions by mistake

When you delete a hard disk partition with Fdisk, the surface phenomenon is that the data on the hard disk has completely disappeared, and entering the hard drive when unformatted will show an invalid drive. If you understand how FDISK works, you'll know that Fdisk just rewritten the main boot sector of the hard drive (0-side 0-Channel 1-sector) In the content. Specifically, delete the hard disk partition table information, and the hard disk of any partition of the data has not changed, can mimic the above partition Table error repair method, that is, to recover the partition table data can restore the original partition is the data, However, this is limited to partitioning or rebuilding partitions. If you have already formatted the partition with format, after you restore the partition, the partition data is restored in the following way.

10. Error-formatted hard drive data recovery

In the DOS high-version state, the format operation is set up by default to restore the formatted disk information, in fact, the DOS boot sector of the disk, FAT partition table and catalog table all the contents copied to the last sectors of the disk (because the latter sector is seldom used), The content in the data area does not change at all. This allows you to restore the original file allocation table and table of contents by running "Unformat C:" To complete the recovery of the hard disk information. In addition, DOS also provides a miror command to record the current disk information, for formatting or deletion after the resumption of use, This method is also more effective.