Each kind of backup or archival store solution has its own
reliability issues. Now, USB sticks fail on a regular basis,
with seemingly no warning at all. And while some of the
data recovery firms claim to be able to recover data from
them, consider that your data would be stored inside an
extremely high density semiconductor. Something that is not
easy to "open up" and service. The only data recovery they
can do, is replace the controller chip next to the storage
chip. If the storage chip itself has a problem, opening
the chip is probably not a service they'd offer.
http://en.wikipedia.org/wiki/Image:DSCN0411.JPG
A hard drive is more reliable, as long as you don't leave it
running all the time. A hard drive is rated typically for
50,000 minimum start/stop cycles, so that tells you how many times
you can plug it in and do a backup. The only limitation here,
is the perception that the drive could die from a stiction
problem if left unused for too long. (In other words, if you
unplug it and leave it for ten years, we don't know whether
it will spin again or not.) I tend not to believe that, but
drives do have different construction techniques. Some have
a landing ramp for the head assembly, so the heads are not
necessarily resting on the platters.
Optical media has its own issues. Some suffer from "rot", and
the rot can happen in a period as short as a couple months.
So the answer may be to use two backup mechanisms.
For external hard drives, I like to purchase my own enclosure,
something with a fan, and then buy a drive to put inside it.
It only takes a few minutes with a screwdriver to assemble.
You can go through the reviews of the enclosure, to see
whether it is a good one. Same goes for drives - check the
reviews to see if there are any new failure trends. (For
example, there have been a couple higher density Seagate
drives, where the motor jammed solid and wouldn't spin any
more.)
Example of an enclosure with an integrated fan. The fan
cannot be replaced. Some have a replaceable fan (40mm).
Read all the reviews, to get some idea what to expect.
This is an IDE, whereas a SATA version would be more appropriate
in today's market.
http://www.newegg.com/Product/ProductReview.aspx?Item=17-145-656
This one has a 40mm on the back for cooling. I've had to replace
a few fans on mine, and this form factor was pretty easy to deal
with. A local electronics store (not Radio Shack) sells good fans,
and once I put a good fan in, I never have to service it again.
http://c1.neweggimages.com/NeweggImage/productimage/17-145-655-03.jpg
In terms of interfaces, a USB2 drive gives 30MB/sec best case.
Firewire may offer a slight bit more (more efficient protocol). The
best is ESATA, as then only the media inside the drive is the
limitation. For each, you need a port on the back of the computer
to take it, and USB2 is most likely to be available on all
your computers. Whether a lot of speed is needed, really depends
on the backup software. (I've had some software that only managed
5MB/sec backup speed, so just about anything can deal with that.)
I personally would not use a USB2 flash stick for backups, because
they tend to drop like flies. There are two kinds of chips
used, SLC and MLC. For highest density at lowest prices, they
use MLC, and for at least some people, they get very few usages
before the thing is toast. (Also, don't buy them from Ebay, because
there are a lot of capacity hacks done to the sticks, to make them
look bigger than they really are.)
http://en.wikipedia.org/wiki/NAND_flash
Paul
