Bad blocks hinder EDB file transfer…

Our client approached us with a huge archive of LTO3 data cartridges created in Symantec Backup Exec. The tapes contained their Microsoft Exchange database files (EDB) and they were looking to restore this after their Exchange Server failed disastrously. Faced with data recovery from the RAID or a full restore from their LTO3 backup, they decided to opt for the tapes. Given the damage to the RAID, it was deemed unlikely that recovery would be 100% successful.

Although the tapes had been verified before writing, when the client tried to restore their tapes bad blocks meant that their usual restoration methods were impossible. LTO uses verify-after-write technology to check data as it is written, hence the client did not need to enable this feature in Back Up Exec. Put simply, the LTO drive has a read head following the write head to verify, or read back data instantaneously. This automatic check-summing makes archiving more than three times faster than archiving to a hard disk drive. Whilst the tapes had verified fine, bad blocks had somehow affected the tapes and this may well have been attributable to the LTO tape drive.

Several back up ‘save’ sets were spliced together from different tapes to create a consistent data set from which to restore their EDB files. All extracted data was validated by byte-by-byte recalculation of block and stream checksums and verifying them against the original error checking codes on tape.

From here the client requested individual mailboxes in the form of PST (Outlook Data) files. Using data recovery software we were able to convert their EDB database files into corresponding PST files, extracting all the mail components in their original format.