Hi, tabanna!
Trying to kill the keyboard, tabanna ([EMAIL PROTECTED])
produced 0,3K in 14 lines:
> Could a CD rw drive be considered a superior solution for all backup
> needs, being Faster, and more Reliable ?
Well, I won't comment about reliability, as I have no hard data.
I'll just mention that on a CD-ro (especially a 'burn yourself')
the information is in the thin film on the top. Take a key
or another sharp object and scritch on the top of a CD you'll
no longer need and see the data come off :-)
Faster ... what speeds do you get these days? 2x or 4x, that
is 300 to 600 KB/s, which is in the range of DAT I or DAT II
streamers, give or take a bit.
For a complete backup solution you'll want anything between
3 sets of media (if all you need is 1 complete backup, one
older complete backup and one to be overwritten) and probably
some more smaller sets for differentials ... up to 'every
day a complete backup, every 4 hours a differential backup,
and noting ever gets thrown away'.
In the latter case the initial cost of the backup engine (drive,
burner, slave with pencil & paper, ...) does not count much, as
the running media costs (tapes, rewritables, paper & pencils,
...) will be the bulk of your costs. Now, how cheap do you
get $YOUR_AMOUNT_OF_DATA MB of $YOUR_BACKUPMEDIA?
In other words: AFAIK tapes are still the cheapest things
around with media costs about $0.0024/MB for DAT I (2 GB)[1],
and getting even cheaper for bigger tapes ($0.0018/MB for DAT
II (4 GB), ...). A Rewritable is smaller and more expensive,
I don't know current prices, so let's guess ... $10 for 650 MB,
thats $0.154/MB. I currently estimate *my* *home* system to
contain about 2 GB of data with the need to back up, so with
5 sets that would be ...
5 * 1 DAT I tape == $25 5 * 3.1 CD-RW[2] == $200
or, if I compress data, using e.g. afio (which can compress
per file) or the inbuild compression in my DAT I:
5 * 1 DAT I tape == $25 5 * 1.55 CD-RW == $100
Now, that's only $75, providing my cost calculation was correct.
If the CD-RW is a bit cheaper than the tape drive, that's
probably OK, but I cannot make automated backups: someone has
to change the CD-RW at some time![3]
Assume now I had much more (important) data to backup, say 15 GB
(say, compressed). The process would probably mean changing
tapes or CDs, anyway, and a set would be 4 DAT II tapes or
24 CD-RWs. On fairly static data quite a few differential
backups would probably fit on a single CD-RW, but still the
CD-RWs would be hard to manage, and a single set would cost
$30 for the tapes ($40 if you used 8 DAT I tapes) or $240 for
the CD-RWs. That's a big difference, especially as you'd want
3 or more sets, it could even pay the DAT II tape drive ...
Now assume volatile, but important data. With a 2 or 4 GB tape
you should get enough place to put a differential backup on[4],
even though you'd probably need 3-6 CD-RWs for a simple diff.
backup.
Now again assume data like mp3 or pictures which are somewhat
transient on the HD but could find a permanent (and immediately
usable) place on a CD-R or CD-RW.
That shows:
If you have small data sets and need few media and/or need
the direct access and/or possible filesystem on the CD-R(W),
you might be well-off with that system. If you have larger
amounts of data and a need for more media you'll get it cheaper
and with less hassle[5][6] with tapes.
But then you may very well have reasons to do it differently,
owing to special circumstances.
-Wolfgang
[1] local prices
[2] You'd want complete sets, so you'll need to buy 4 per
set, even if you loose 90% of one CD-RW
[3] which *is* an enourmous drawback, considering that lazyness
is the greatest enemy of backups! *I* want everything
automatically done, so I can basically forget about backups
... only then I will get them regularly. Yes, I am lazy.
Lazy enough to spend time to automate such stuff.
[4] unless you have more files changed than will fit in 2-8
GB (depends on size and compression). If you fall in
that category, you'd probably want a bigger/faster drive
anyway ...
[5] Size of the set, media changes, transportability, ...
[6] If you have really large amounts (10's of GB or in the TB
range) of data, there are autoloaders and even tape robots!
