Re: Please suggest archive/backup solution?

Douglas Mayne wrote (in part):
On Fri, 22 Jun 2007 22:19:53 -0700, Sarah wrote:

Thanks for reading. We have rented space at a computer center, 3
terabytes. We put our data there, and pull it down to workstations as
we need it, and we depend on it as a backup for ongoing processing
too, occasionally backing up current work there.

The problem is, they are unreliable....down often, and with nobody
really supporting the system. We want to bring our archive/backup in
house. But, we need to do it as cheaply as possible.

Looking around I see DAT tape backups for a few hundred. It's OK if it
takes overnight to put some data in our archive, and to pull some data
out to work on. We just need a safe, cheap solution. Usually we keep
things currently being worked on on our workstations, and only
occasionally need to swap to the archive for new data. We put new data
in the archive 2 or 3 times per week. Is this what you would
recommend, or are there other better options?

Many thanks for any suggestions.....

Sarah

This type of question comes up fairly often. I have generally recommended
hard drives to hold multigigabytes of data. The continued increase in hard
drive capacity has only strengthened this opinion.

Magnetic hard disk capacity continues to increase rapidly. The 500G SATA
drives have attractive operating parameters (capacity, transfer rates,
etc.) and price per gigabyte continues to drop. As capacity continues to
increase, it won't be long until it is common to quote cost per terabyte.
This is really remarkable considering I once paid more than $500 for a
70MB drive. Now, you could build a simple networked computer with a
couple 500G drives gives a terabyte storage solution for less than that.

Comparison with tape...
I realize I am treading on an area which causes religious wars,
mostly because tape has been around for a long time. During most of that
time, tape has been the only practical way to store large amounts of
data. I have a need for a small number of terabytes. That amount of data
fits within the current generation of hard drives. So, the first question
to answer is to define your long and short term storage requirements. An
LTO tape solution is probably still the cheapest way to store a large
number of terabytes. BTW, LTO tape appears to be much more reliable than
DAT. People who like tape concede that DAT isn't great, and won't mess
with that.

I am one who likes tape, even though I do not disagree with what Douglas
Mayne wrote above. I cannot stand DAT-type tape drives. They have more
capacity than ordinary audiotape cassette drives that were once used in the
mists of time past. But that is about it. I have never used LTO tape, so I
cannot comment on it beyond what I have read about it. It is much more
expensive than DAT tapes. I suspect it is much more reliable, too. I happen
to prefer Exabyte VXA type tape drives.

There are advantages to hot swappable disk storage for backups. First of
all, if you want to restore just one file, you can do it very fast, whereas
if you are using tape, the file you want is, by Murphy's Law, at the other
end of the tape in question.

The big advantage of tape is that tape cassettes (for VXA drives, in any
case) are still cheaper than hot swappable hard drives. And you can put more
tapes in your safe deposit box than you can hot swappable disk drives.

So which to use depends on why you are doing backups. My restores usually
are made the same day as I ruin or delete a file that I want back right
away. Any disk backup would do for that, or any tape, but restoring from a
backup disk would be much faster.

However, if you are like me, sometimes you destroy a file on day 1 and do
not notice it until day 41 or something. Now, while I do not have 41 backup
tapes, I do have 23. 6 for days of the week, 5 for weeks of the month, and
12 for monthly backups. That way, if I screw up and notice it within the
week, I can surely get it back. If not, I can get to the nearest week if I
know that, and the nearest month after that. If I do not notice by then, too
bad for me. Although I could (but do not) make yearly backups. Were I
running a CPA or legal firm, I suppose I would keep yearly backups forever.
I do not see any practical way to put 12 hot swappable hard drives in a safe
deposit box. and I doubt Douglas Mayne would seriously suggest that.

So first, you need to answer the question, why am I making these backups.

Hard drives have other advantages over tape, too. You can't boot from
tape, AFAIK.

Actually you can (or could), with some tape drives. The HP C1599A would do
that. If you power on the computer while holding the button on the tape
drive, it will make itself look like a CD-ROM drive and boot from it. This
was used for their "One Button Disaster Recovery" feature allowed you to
write backup tapes so that when the disaster came, you could replace your
hard drive(s), or your whole computer, stick the tape in the OBDR drive and
boot it. It would reformat all the drives as they were, and reload
everything to just before the disaster occurred. At least in theory. They
may have put this feature in other tape drives too.



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