Shulou(Shulou.com)06/02 Report--

Many engineers have such doubts as to whether the data can be recovered after MDisk reconstruction. What should be done to recover the data? In this paper, we take IBM V7000 storage as an example to explain in detail the recovery method of data loss caused by the reconstruction of a certain MDisk. The storage in our case lost the VDisk in the corresponding storage pool due to MDisk reconstruction, which affected the normal use of the Oracle database in the upper Solaris operating system.

1. Prophase backup method

Since the analysis and recovery of the equipment are not operated on the original equipment, first of all, we need to link all the VDisk related to the Oracle database to the backup server in read-only mode, and use professional tools such as dd or Winhex to backup the mapped VDisk in read-only mode. Then sort the reconstructed MDisk member disks and remove the IBM V7000 enclosure in normal mode, connect the removed hard disk to a professional device, and do a full mirror in read-only mode. Wait until all backups are completed before all links and physical hard drives are restored, and post-analysis and recovery are not operated on the original device.

2. MDisk and VDisk recovery methods.

A. analyze the data of the backup MDisk member disk in read-only mode to determine whether a large amount of data will be lost due to MDisk reconstruction.

B. analyze the data distribution rules of RAID6 after reconstruction, and calculate that the double checks of RAID6 are written to the specific location of the hard disk.

C. The data areas destroyed by RAID6 double check are combined with the data distribution rules of RAID10 to restore the pre-reconstruction MDisk as much as possible.

D. Analyze the underlying volume of the recovered MDisk, take out the data MAP in reduced mode, and verify whether the data MAP is normal.

E, according to the reduced mode algorithm combined with data MAP, restore VDisk as much as possible.

F, check whether the restored VDisk is normal, otherwise re-analyze the steps of AME is correct.

3. Database file recovery and database file repair

a. Scan the Oracle database page features of the recovered VDisk and other undamaged VDisk, and generate the feature set of the corresponding database files.

b. According to the feature set of the database, the data distribution MAP of the database in all VDisk is analyzed.

c. Restore the database files, and use the self-developed Oracle database detection tool to check the file consistency of the restored database files.

d. If the database file detection is normal and the database structure is complete, try to start the database instance and monitor the status at the same time.

E. MOUNT database, view the database file status information, view the overall status of the database. Try the OPEN database and do instance recovery.

f. Verify that the exported data is correct, otherwise repeat the Amure operation until the data is correct.

4. Estimate the success rate of MDisk reconstruction data recovery.

Because a MDisk in the IBM V7000 storage has been rebuilt, the upper VDisk and Oracle databases cannot be used properly. If the rebuilt type of MDisk is RAID6 (formerly RAID10), it will result in partial data corruption. In a worst-case analysis, the data of 2 disks (double parity of RAID6) will be corrupted (in fact, not completely). In terms of damaged VDisk, the data integrity will exceed 75%. The upper Oracle is composed of multiple VDisk, so the data integrity of the upper Oracle layer is more than 95%.

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