From what you say about your enviroment I would go for 9940B

When I say that 9940B are slow compared to 9840B it's on average access 
time. Except from that 9940B's are much faster then 9840B's.

If your installation is not using/needing a lot of very fast restores of 
smaller files 9840B's is the fastest drive you can get.
Look at this document for from StorageTek 
http://www.storagetek.com/pdfs/October_18_2002_external.pdf
It basicly takes longer time to get the 9940B's to start writing and 
reading then 9840's, but when they write or read they are a lot faster.

What we have done to keep the time lost on access down is to keep the tapes 
a little longer in the drives after a backup job ends so that the chances 
are bigger that the next job will not have to wait for a new mount.

By they way if you expect to "top off" at 10TB in 24 months I think that 
statistics normaly shows that when we think we can plan and calculate how 
much data we will have in any give time we almost always are far below what 
will realy happen.

Another thing. I don't think you should wait for 9840C's. From what you say 
you need is't not prime access time but prime capacity and that is the 9940 
series of drives. And plan for libraries that scale (if you are not already 
using 9310's)

But more importend. What is your restore needs?

If they expect that you can recover a 2 TB LUN with 8.000.000 files in less 
then 3 hours the task is a little different then if you need to do the same 
job in less then 24 hours. Restores is what realy dictates how you need to 
take your backups.

/johnny


At 16:52 21-11-2002 -0600, Paul Bleimeyer wrote:
>Johnny, David, others,
>
>Thanks for your comments. I am currently looking at a high growth
>environment with a limited
>retention window. 90days worth of backups with a little over 2gb of data.
>Currently we have
>4 drives running in a SSO environment over FC which works pretty well once
>you get all the
>the WWN's locked down to a specific Scsi id and held there. My main issue is
>that with 10
>upstream servers, it takes a bit of juggling to make sure everyone gets a
>drive at night
>at the right time and I don't see my growth tapering off until around 10TBs
>sometime in the
>next 24 months. Backup performance ranges from 7Mbps on highly fragmented
>arrays in the SAN
>with lots of small files and thousands of folders, to 10-11Mbps when we hit
>the large files
>and department style folders with large amounts of presentation data and
>images.
>My concern is that I am seeing the type of data we are handling is changing
>over
>time, which an increasing amount of it being somewhat uncompressible.
>
>Johnny, You mentioned that I might find the speed of the 9940B somewhat slow
>in comparison
>to the 9840s we have now. Can you give me an idea of slow? I know we are
>going to see a 10x
>increase in capacity (uncompressed), but at what performance penalty? I
>would rather
>wait for 9840C's since it would theoretically allow me to reuse my existing
>tape files, but
>I am very concerned that we might not make it if the growth continues. I
>will have to
>rethink at my buffer settings again on my media servers as well. I think
>there might be a bit
>more I can squeak out of the drives for performance.
>
>Our compression has been averaging around 1.6-1.7 to 1 right now, where as
>it used to be right at
>2.0 to 1.
>
>Respectfully,
>
>Paul
>
> > -----Original Message-----
> > From: Johnny Oestergaard [mailto:joe AT joe DOT net]
>
> > The best we get at the moment on the drives is around 13
> > MB/s. We have seen
>
> > Moving from 9840 to depends mostly on what kind of needs you have.
> > Using 9940B's will give you a lot more data in your library
> > then using
> > 9840B, but remember if you are used to the mount times and
> > seek times on
> > 9940B you will think of 9940B as slooow.
> >
> > In a HSM system with a lot of tapemounts 9940B could slow
> > down your system,
> > but if what you have is a "normal" backup/recovery senario
> > you could end up
> > with a faster total system performance with 9940B.
> > 9940B is faster then 9840B, except for mount/dismount and
> > seek, and you
> > need less mounts to backup eg 1 TB data to 9940B then to 9840B.
> >
>
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