SUMMARY: Backup of non-4.2 file systems

From: Torsten Lif (
Date: Tue Sep 29 1992 - 08:48:58 CDT

As always this list comes up with good replies in record time. I asked
how to backup a database that uses a non-4.2 SCSI disk partition and
specifically asked if the data output by dd would be useful. The
net.response is that I'm in luck - since SCSI drivers "hide" the error
mapping of the disk at a lower level, dd sees it as an error-free
contiguous data space and a new dd returning the data to it will work
as long as the disk is of the same type and geometry as the old one.

Of course, this provides only "crash backup" and gives no means to
restore an individual file in case a user makes a mistake. The only way
to achieve that is to run the application itself and tell it to
"export" the entire database. Apparently there exists no "batch" mode
in our specific little problem-child so this has to be done by an
administrator manually. However, I think we can reach a compromise
where "we" (the UNIX administrators) do a "dd" nightly and the database
administrator runs a manual "export" whenever he remembers to...

Other considerations:

    I forgot to include a blocking factor for dd.

    I have to make absolutely sure the filesystem is static before
    starting dd.

    Since the disk is likely to be mostly empty, it's smart to pipe the
    data through compress before storing on a regular UNIX file.

Thanks to those who have already answered and to those whose replies
come in after I send this.

 Torsten Lif
 Ericsson Telecom AB, EO/ETX/TX/AD
 Phone: +46 8 719 4881

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