Re: Tape drives -- Recommendations?
2008-10-15 12:53:52
Chris Hoogendyk wrote:
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.
SCSI, plain jain SCSI. SAS is a good option, Fibre channel is a bit
outside. The biggest thing with that is I would add to the cost to get a
good SCSI card, since none of my servers, oddly enough, have a SCSI Bus.
Almost all of the Tape Drives I have seen are SCSI, so I was trying to
look outside of the box. That is the only base on the preference on
that. With the network side, I do understand that, even as I have gig
networking, I burn only 25MB/s at max across it (strangely enough it is
both wired and wireless that burns the speed like that) since I am using
backuppc to gather all my computers into one archive/backup, since it
took care of a more immediate problem.
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.
Breaking up full disks and incremental backups with Amanda looks easy
and I have gotten it to work in single tape mode prior, so it is pretty
good. Now when the tapes are 4GB max... well that sucks with large data
over the time, though it isn't like I had a shortage, just no changer.
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.
I have just recently started playing with vtapes, and haven't gotten it
to work just right yet, but that is, once again my fault. This server is
a little on the redundant side as it is, with Raid5 as the main disk's
protection scheme, and I want to get this stuff onto tape as a backup of
a backup.
So far all the answers I have right now are pretty good. All in the
under 10k side, which giving this as, oddly enough, a home based budget,
will take a bit to get I am rather pleased with it.
Thanks for the good answers so far, and I do look forward to other's
suggestions as well.
~Seann
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