Date: Fri, 23 Apr 1999 16:08:32 -0500 From: "Mike Avery" <mavery@mail.otherwhen.com> To: freebsd-questions@freebsd.org Subject: Re: Tape Backup Message-ID: <199904232122.QAA03394@hostigos.otherwhen.com> In-Reply-To: <199904232042.PAA04533@coffee.veryfast.net> References: <Pine.BSF.4.03.9904231321410.29524-100000@resnet.uoregon.edu>
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On 23 Apr 99, at 15:46, John McNamee wrote:
> On 23 Apr 99 at 13:22, Doug White <dwhite@resnet.uoregon.edu> wrote:
>
> > > Is there tape backup software for FreeBSD that in addition to backing
> > > up UNIX will also backup NT Servers with Registry and Microsoft SQL
> > > Server on a live system. I am using BE for NT currently but would like
> > > to move yet another network function to BSD.
> >
> > Backing up SQL databases requires the backup program to have initmate
> > knowledge of the DB system so it can handle the hot backup properly. I
> > doubt it can be done from remote reliably.
>
> FYI...
>
> The way this is handled in the NT and Netware worlds is that the backup
> software doesn't directly access the SQL database files. An agent (e.g.
> daemon) runs on the database server machine, and it handles all the
> details of database I/O to allow hot backup and restore. These agents are
> all proprietary -- you need one specific both to the database and the
> backup product. Database agents are typically a high priced add-on and
> not part of the basic backup software.
That's one approach. Stac's Replica, Columbia Data Product's
SnapBack Live, St. Bernard's Open File Manager, and Computer
Associates Open File Agent use variations on a different approach
that is a bit more generic. I think Seagate Software has a similar
approach, but I haven't looked at it.
At the start of a backup (and they all seem to have different ways of
detecting it), they setup a change file. When any disk activity occurs
that would change the disk contents, the old data is written to the
change file, and the new data hits the disk. If the backup program
asks for data, it get the data from the change file if it's in there,
otherwise it gets data from the disk. Any other program that asks
for data gets it from the disk. This is tracked at the sector level.
Some of them protect against file deletions - that is, if you delete a
file, the file is moved to the change file. Some don't. I prefer to
save the files. All these approaches *SHOULD* work with any data
base. The files *SHOULD* be restorable in the same condition as
when the backup started. Sometimes the implementations leave
someting to be desired.
Stac and Columbia bundle the open file product with their backup
software. The other vendors sell it as their main product, or as an
add-on to their backup products.
Mike
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