Backup choices, was RE: OT: tape backup

[KirkE paccessglobal com]

Greetings all,

There are a significant number of choices for backup devices, most of which
remain magnetic tape of one kind or another, but also optical storage
(Phasechange, Magneto Optical and more recently CD-RW/DVD-RW and DVD-RAM,
all based on phasechange). The cost of the drives and the inherent tradeoffs
in any of these solutions should be considered. Their primary use will
determine the best solution, though its pretty clear that none of the backup
tape or optical solutions will be sufficient at a low price point to backup
very high capacity magnetic disk drives and this trend seems only to be
increasing. 

You are also better off tarring up and gunzipping the whole volume you want
to backup before running your backup utility as the 2:1 compression of the
tape drives compression engine is no-where-near as fast as a drive with
compression turned off and manually zipping up your archive to upwards of
50:1 compression ratio.

For home use at a low cost, the Travan drives (essentially QIC reborn), DSS
4mm drives and the newer low cost drives like the Onstream (deceased) are
the sweet spot for cost/drive capacity but with the exception of DDS-4 and
possible Onstream, these are relatively slow and use much more fragile media
with a much shorter useable lifespan.  If an occasional full or incremental
backup is needed, a Travan or DDS-3 tape drive should be fine, provided you
can exclude anything not necessary for recovery or which can be easily
re-installed from disk (i.e, don't backup a support directory full of app
bins or utils). 20-24GB compressed rates are the standard fair.

I have yet to see anyone with those new 80+GB drives in their new desktop
home computers have a suitable backup solution in place or even a plan to
backup said drive assuming they actually filled it.  Backing up more than
about 30GB today requires much more expensive drives that are priced well
outside of the same commodity markets that sell 80-90GB disk drives or
bundle them in low-cost home computers. Running the backup set across many
tapes is a possible solution, but requires an amount of operator
hand-holding to swap tapes.  Backup times and restore times on such low-end
drives is also pretty staggering.  One wonders if they could not make a
business case that a 120GB disk drive should NOT be made available before a
suitable optical or tape backup device is introduced at an appropriate price
to actually USE that capacity safely.  On systems where you can stripe data
in a RAID of one level or another, chances are you also have a tape library
or an autoloader to take the work out of backing up the full capacity of the
array.  The cheapest tape autoloaders that can be had are either used DLT or
DDS-4.  I've seen a few at www.teamexcess.com (HP drives) with a 5 tape
magazine and DDS-4 capacities (40GB per tape, compressed) at $250.00.  These
are a rarity.

Until blue laser becomes practical, optical drive technology is way behind
the curve compared with magnetic storage.  DVD-RAM could easily scale to
50GB per layer, 100GB per side (dual layer, dual sided), but the DVD-RAM
drives are still single headed and can't read the capacity on the other side
of the media without flipping (identical to the MO and old phasechange).
Optical is still a better choice than tape for random access, but data files
generally aren't that dependent and the idea of HSM (Hierarchal Storage
Management) to migrate files from "online" storage to "half-line" optical
storage (usually an optical library) and then to "offline" tape is almost
dead with single drives approaching 180GB on a half-height 3.5" drive. For
fast access to multimedia files and long storage life, its hard to beat
5.2GB DVD-RAM, particularly at a fraction of the cost to the somewhat faster
MO 5.3 drives. Also, these disks have a total immunity to EMI, good if
you're planning on taking one into space or surviving a nuclear attack. :)

The price delta between an LTO or DST tape drive and a single Seagate 15K
180GB disk is enormous. I'd petition my congressman, if I thought it would
help.:)

--Kirk