Shulou(Shulou.com)06/03 Report--

Description of server data recovery failure

Today introduces a server data recovery case, through today's case mainly introduces the server in the partition can not be mounted in the case of how to fully restore the data in the server, for the server data recovery without backup has a certain help. Here is a brief description of the specific failure of the server in the case:

The server that needs data recovery this time is a certain brand 730 series server, the storage array model is MD3200, the series storage, the allocation lun capacity is 8TB, the operating system version is linux centos 7, uses the EXT4 file system. Due to unknown reasons, the server suddenly shuts down during operation and cannot be started. The server administrator can start the server after repair, but the original partition in the server cannot be mounted. The administrator repaired the partition that could not be mounted by fsck and mounted it to check the data, and found that some files were missing. As a large amount of important data was stored in the server, the administrator decided to seek the help of the data recovery company. After comparing several data recovery companies, the administrator chose a data recovery center in Beijing. After receiving customer consultation, the data recovery center arranged for the server data recovery engineer to come to the door for fault detection.

Second, failure analysis of server data recovery.

The server data recovery engineer remaps the failed server to the dedicated data recovery backup server in read-only mode after the server data recovery engineer arrives at the customer site, and then uses the data recovery tool to mirror the customer failed server to the data recovery backup server in sector form. The data recovery engineer analyzed the data in the backup server and speculated that the failure may be due to the abnormal power outage and shutdown of the server caused by the unstable voltage in the computer room.

Third, the principle of server data recovery

The server data recovery engineer carefully analyzed the underlying data of the server and found that the sudden power outage of the server led to the destruction of the directory entry, but the underlying data still existed, and the data recovery only needed the engineer to repair it manually. Due to the fsck repair of the file system by the server administrator, the damaged directory items failed to be repaired and named after the directory node number and stored in the lost+found file directory, and then cleared the data area index corresponding to these directory entries. This is why some files are missing.

In this case, if you want to recover the data, you can troubleshoot the file system and file type of the deleted virtual disk file in the free space of the vmfs volume, match the fragments and re-merge, and finally recover the deleted virtual disk file.

IV. Server data recovery process

Because the server that the customer needs for data recovery uses the EXT4 file system, which is characterized by the fact that the node information of the file will also be cleared after the file is lost, the method of restoring according to the node information can not be used in this data recovery, but should match the file name under the lost+found directory according to the node number of the lost file directory. Because the naming rule of the file under the lost+found directory is the directory item node number of the file, the server data recovery engineer will extract the directory item node number and correspond to the file name under the lost+found directory one by one, then you can restore the original directory structure of the server.

According to the above data recovery idea, the server data recovery engineer analyzes the underlying data of the image file, scans the area of the directory item in the underlying space, counts and records the node number and other information of the directory item, and then integrates and matches the statistical directory entry and node number according to the file system information in the server disk, and finally matches the file record number in the lost+found directory. Finally recover the lost data in the server.

Summary of server data recovery

Finally, a brief summary of the server data recovery process, the server data loss is first of all due to abnormal power supply caused by the abnormal shutdown of the server damaged the file system, and then artificial fsck repair led to the loss of file directory structure. The data recovery center has sufficient data analysis and recovery ability for the underlying structure of the EXT4 file system, and has rich experience in server data recovery. The whole data recovery process is very smooth. The client server administrator verified the data and confirmed that the data recovery was successful, and the server data was restored 100%.

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