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Re: Tape drives -- Recommendations?
2008-10-15 14:43:30
Seann Clark wrote:
All,
I am fairly new to the list, not so new to Amanda (I usually troll
IRC when I am looking for help half the time) but I want to poll the
group for suggestions to aid in what I am looking into as well. I have
a system currently that has 3.12TB of data, which I would like to
start backing up regularly, and soon will increase that to a larger
number as well. I am looking for a good service tape drive that can
take care of the physical offloading of backups, and that plays well
with Amanda. I have an old SCSI HP SureStore that I can never get to
really back up to (Pity it was a nice drive for the time, esp when I
was maxed at 700GB) though it can read the tapes, write to the tapes
through Amanda, it just dies partially through and freezes up the
drive. What I am after though is a backup system that is tape based. I
would prefer non SCSI, but I can work around that.
The other alternative I am looking into is getting a large external
case and cramming it full of 1TB hard drives and using that as backup,
but I would like a tape system that works well. I haven't gotten that
portion to work too well in the past, but since it was a first time
doing it, I am very sure it was a fatal user error that was preventing
it from happening.
It has a huge amount to do with budget.
Being in a budget conscious department, I settled on a Sony LIB-162A5.
Ballpark cost around $5k. Less if you get good discounts. It uses AIT5
tapes (400G native), comes with one drive but can take a second, holds
16 tapes. The somewhat lower cost comes from being a carousel mechanism
that is less complex than the typical robots. That also means it is more
reliable, but less expandable than the popular lines of robotic libraries.
I think most people are going with LTO. I chose AIT because I liked the
technology. It isn't as fast as LTO, but it doesn't shoe shine. I hear
plenty of horror stories of people who get a really fast LTO drive and
find that they aren't getting any throughput. That's actually because
the computer they configure to go with it can't maintain the data
throughput that the tape needs, so the tape goes into shoe shining, and
the throughput drops even further to dismal levels. Of course, if budget
is not an issue, and if you understand your hardware configuration well,
then you will configure a backup server that has the capacity to pump
data to the tape and keep it going. I have no trouble keeping the AIT5
going at its full rated speed.
Why not SCSI? Most of the tape libraries are SCSI (either directly SCSI
or via SAS or Fibre Channel). Mine is LVD320 SCSI. I'm not sure what
alternative you are thinking of. Whatever you choose, you have to think
about throughput. Figure out how much data you are planning to transfer
and then calculate optimal times. You won't typically get optimal, but
it will put you in the right ballpark. Be sure to account for bits
versus bytes in the various transfer technologies. Network stuff is
going to be bits, internal bus transfers are typically bytes. So, I run
Gigabit network and my AIT5 will do 25MBytes.
Fortunately, Amanda will smooth the demand over your dump cycle. So, if
you are trying to do 3.12TB total, and you break that up into many
DLE's, then you may only be averaging 500GB a night or even less,
depending on your dump cycle. I'm sure you already know that, but it is
a significant part of the calculations and a real advantage over other
backup software.
Of course, it certainly doesn't hurt to do both vtapes and tapes. I'm a
big fan of redundancy, which is why I run a long tape cycle and have
dual holding disks.
--
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Chris Hoogendyk
-
O__ ---- Systems Administrator
c/ /'_ --- Biology & Geology Departments
(*) \(*) -- 140 Morrill Science Center
~~~~~~~~~~ - University of Massachusetts, Amherst
<hoogendyk AT bio.umass DOT edu>
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Erdös 4
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