BSD/OS Drive Mirroring -- Backing Up Disk To Disk

Where can I get a script that allows one to easily dump and restore a boot disk to an identical disk, so I can boot off the backup disk once the master disk has failed?

BSD/OS does not have support for software mirroring of disk drives. On machines where multiple boot devices can be easily configured from a serial console (e.g. SPARC based machines), it is sometimes desirable to have a manually invoked disk mirroring processes, to snapshot all the data from the master disk to a second device in the same machine.

Machines that are deployed into remote locations (e.g. colocation facilities) are often candidates for this type of semi-automatic disk duplication. While not as robust as software mirroring systems where the data is maintained on both drives in parallel, this type of arrangement is still practical in some circumstances.

The following script duplicates the data on the source disk to the destination disk. It runs through the following operations:

• spin up the destination disk
• newfs the partitions of the destination disk
• mount the destination filesystems (asynchronously)
• dump the source filesystems, restoring onto the destination filesystems
• fix the fstab on the destination disk so it can be used as a boot disk
• unmount the partitions of the destination disk
• turn on softupdates on the partitions of the destination disk
• spin down the destination disk

The script can be accessed here: http://www.pix.net/staff/lidl/nsfaq/bsdos/dodiskback.

Known limitations

• doesn't do MBR records on FDISK partitions (x86 only)
• doesn't do boot blocks
• doesn't do disk partitioning

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Kurt J. Lidl
lidl at pix dot net
Last Updated: $Date: 2004/05/18 02:21:37 $