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1. Description of server data recovery

The server that needs data recovery uses Linux operating system and EXT4 file system. Three KVM virtual machines on the server were deleted due to the intern's error. Each virtual machine on the server contains a disk file in qcow2 format and a disk file in raw format with a size of about 1.2T. It is mainly necessary to restore the disk file in raw format.

II. Restore the server virtual machine process

1. Analyze the EXT4 file system in the server and locate the deleted virtual machine disk file node.

2. Get the residual index information of disk files.

3. Check the correctness of the residual index information and repair the indexes that are not seriously damaged.

The picture shows the obtained index and other information:

Figure 1

4. After the repair, the remaining indexes in the server are parsed, and the virtual disk files are extracted from the volume where the virtual machine resides.

5. According to the extraction of virtual disk files, get the free space in the volume that is not indexed.

6. Check the correctness and integrity of the extracted disk files.

7. Get valid information from free space and try to repair virtual disk files (such as nodes, directory items, database pages, etc.).

The picture shows the extracted free space:

Figure 2

III. Results of data recovery

1. Due to the loss of the index, the extracted virtual disk file is not complete. For the database server, if the database file is lost, the database page can be obtained from the free space to repair the database file. However, as part of the page area is covered and occupied, you can only fill as many pages as possible.

2. In the case of the loss of nodes and directory items in the server where the program code is stored, if the node or directory items remain, you can try to make up the nodes and directory items. However, it is found that the nodes and directory items of some files are lost at the same time, which cannot be made up according to the characteristics associated with the nodes and directory items. In addition, according to the characteristics of the program code file, it does not have a certain regularity, if its data area is lost, it can not be made up.

The figure shows the recovered partial directory structure:

IV. Data verification

After trying to patch the virtual disk file and the database file in it as much as possible, the data is verified by the customer. 90% of the server data is recovered, and the data recovery is successful.

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