Disaster Recovery Testing — 8

Disaster recovery testing continues with rebuilding both office desktop hard disks.

There is one seldom used 20 GB partition on the office desktop backup disk. The partition is not modified when accessed. The partition is retained for historical purposes. I do not want to lose that partition.

In this disaster scenario that historical partition would be lost without the clone backup disks. There is a similar virtual machine (VM) that is backed up regularly. That VM could suffice to rebuild the lost partition albeit with sweat equity. While a doable approach, the idea behind disaster recovery testing is to expose potential data loss and minimize disruptions. Rather than deal with a doable but less than ideal approach, I immediately created an image of the partition on both weekly backup disks. The image file backup will suffice because the partition is never modified.

The next challenge is using a 1 TB disk rather than a 2 TB disk.

As might be expected, restoring the original 2 TB partition table failed because the replacement disk is a smaller capacity.

The sgdisk command aborted the attempt to restore the partition table:

Problem: partition 8 is too big for the disk

Partition 8 is the home LAN video collection partition.

I knew of no command options that supported selectively restoring partitions. I could manually create the partition table using the fdisk dump files. Slow but doable. Then I remembered the sfdisk command, which is designed for scripting.

I had no sfdisk dumps. To improve the disaster recovery process, I paused and created sfdisk dump files for all computer systems in the home LAN.

I attempted to use those files to recreate most of the 2 TB disk partition layout.

Restoring the sfdisk dump to a smaller disk again failed. The command complained that Last LBA specified by script is out of range. After some web searching and not finding an answer, on a whim I deleted the last-lba and last partition entries from the dump file. The sfdisk command then succeeded.

I manually created the video collection partition, although at a smaller size than the original. If needed later I would decide how to use additional disks and modify /etc/fstab.

Not a bad start, but more to come.

Posted: Category: Usability Tagged: General

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