Corrupt Backups or Missing Tapes

• Your backup software fails during a restore operation with a message such as:
  • CRC Error
  • Parity Error
  • Invalid header encountered
  • Checksum mismatch
• You've found tapes 1 and 3, but tape 2 is missing or has been reused.

Unfortunately, because of the sequential nature of data stored on backup tapes, encountering logically corrupt data during a restore or missing a complete tape in a sequence can prevent access to any further valid data or files beyond that point.

Some backup software retain catalogues of the data they have backed up and it is sometimes possible to perform a selective restore to circumvent this problem. This is not always possible however.

At Altirium our tape recovery experts have been decoding data from backup tapes for over 20 years and we develop our own software for extracting the original files from within the encoded backup data. The software we develop allows us to overcome the logical corruption or missing data and restore the valid files that may be critical to you.

Between reading the data from the disk to recording it on to the tape, the data being backed up can pass through a complex network of processes. Both logical processes such as backup agents, network buffering, re-blocking, checksum generation, compression and encryption and physical processes as data is transferred over networks and between devices, can all encounter errors.

Many applications attempt to detect these errors and report them at the time of the backup, however this is not always possible. The most reliable method of ensuring the data that has been written to the tape is valid and can be restored is to verify the data immediately after the backup or perform a test restore from the tape. Due to the large volumes of data generally being backed up and the time involved to perform a data verification this is not always practicable or possible.

Checking the backup logs and reports can often help to identify problems before they become an issue.