[unisog] Tape backup solutions

Peter Van Epp vanepp at sfu.ca
Mon Jun 17 15:34:03 GMT 2002

> I think hard drives are cheap enough so you could just use NAS to mirror
> your stuff.  HDs are beginning to get competitive with tapes:
> Tapes		$75/40GB		slow, ~1 year shelf life
> HD		$100/40GB		fast, ~3 year shelf life
> --
> --Patrick Darden                Internetworking Manager             
> --                              706.475.3312    darden at armc.org
> --                              Athens Regional Medical Center

	While this is possible (and in some cases such as petabyte file stores,
the only practical alternative) there are volume and power issues to think
about. Tape takes no power (of course neither does disk that is powered off)
and is much lower volume than tape. This makes multi generations of backup
more practical which can be important when you are defending against a software
error (such as subtle file corruption in the NAS unit that isn't noticed for
several backup periods). Backups aren't only protection against hardware 
failure typically (otherwise raid and friends would be enough usually) ...
	As well a UPS failure that overvoltages (and destroys) your spinning
disk won't affect a non powered tape. Storing tapes off site is much easier
(partly because they are less shock sensitive than disk) as well. While a 
a remote backup site with spinning disk will solve most of these problems (but
not the software error if both NAS units run the same software ...), you may
find the TCO is more than tape by the time you factor in the cost of the 
network pipe between the NASes. There are lots and lots of issues to consider
on a well designed backup system not only the usual one of a hardware disk 
failure ...

Peter Van Epp / Operations and Technical Support 
Simon Fraser University, Burnaby, B.C. Canada

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