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

Raid5 array data recovery case profile

Record a success story today for RAID 5 disk array data recovery. First, let's briefly introduce the basic configuration of servers that require data recovery:

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The customer's server equipment is EMC Storage, a raid5 disk array consisting of multiple stat hard disks in a disk array containing two hot spares. Two of the underlying hard disks failed when the server crashed, and one of the hot spares was activated.

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[Server Data Recovery Routine Detection]

Data recovery engineers from the data recovery center travel to customer sites to troubleshoot server equipment. The server data recovery engineer conducted a simple investigation on the client server equipment and confirmed that the raid5 array was down; the upper lun could not be used normally, and one of the two hot spare disks had been started.

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The data recovery engineer physically checked the disconnected hard disk, and no physical damage such as bad track or head failure was detected in both hard disks. The following data recovery operations can be performed without the need for physical repair.

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Raid5 Data Backup

Before the data recovery operation, all original data on the server equipment needs to be mirrored. In this data recovery case, the server data recovery engineer connects all hard disks to the dedicated storage pool for data recovery in the North Asia Data Recovery Center and performs sector-level mirroring operation on all hard disks.

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[Analyze the RAID group structure of this server]

Server data recovery operations are usually performed based on the recovery raid group, so this data recovery operation also needs to analyze the basic information of the raid array to reorganize the raid structure.

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After analyzing each hard disk, the data recovery engineer found that there was no data in the two hot spare disks in the original server of the customer, that is to say, even the activated hot spare disk did not synchronize to any data, and the two hot spare disks did not actually have any effect. If you want to recover the data, you have to continue to recover the other basic data of the original raid5 array and reorganize raid5.

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[Analyze RAID group dropped disk information]

According to the above data recovery idea, the server data recovery engineer used the self-developed data recovery tool to analyze the basic information of the group of RAID 5 arrays, and virtually reorganized the RAID 5 disk array. Under the raid data recovery routine, we remove the oldest drive from an array of multiple drives that went offline. Usually, the method of data analysis is to compare whether the data on the same stripe of each hard disk is consistent, and to remove the obviously different hard disks for stripe verification until the best state of data recovery is found.

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[Analyzing LUN information in RAID groups]

After successfully reorganizing the RAID 5 array, the engineer starts to analyze the lun information. In this data recovery case, there is only one lun on the upper layer of the customer's server. The engineer only needs to analyze this unique lun information, and then use the RAID data recovery program to parse and export the lun data map.

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Resolving and repairing ZFS file systems

Use data recovery tools to parse and recover the upper file system. The client upper layer uses the zfs file system, and the server data recovery engineer finds that some file system metafiles report errors when parsing the file system, so the data recovery engineer debugs the existing data recovery tool to adapt the program to the actual situation of this data recovery.

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After debugging, the reason for the zfs file system parsing error is that some metafiles in the file system are damaged due to the sudden collapse of the client server, which causes the data recovery tool to fail to parse properly. Server data recovery engineers use manual repair methods for damaged metafiles to ensure that the zfs file system can be parsed normally.

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[Export all data in raid5 array]

Through complete analysis of the file system, the server data recovery engineer finally exported the data in the customer raid array completely, and the customer engineer cooperated to build a data verification environment to verify all the recovered data. After verification, all the data in the customer's original server were successfully recovered. This data recovery was successful.

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