Newsgroup: it.comp.hardware.storage
Titolo: Quantum SuperLoader vs. Overland Neo

I need to move up from an Exabyte Mammoth2  drive to a library system. I've
been displeased by the numerous tape errors from the M2.
I'm looking at two options right now:
1. Quantum ATL Superloader with a SDLT 320 drive. I would get a $2500 credit
on tradeup to the SDLT 600 drive in the fall. The total cash outlay after
the drive upgrade would be similar to the cost of the Neo 2000, but I'd have
to buy new tapes in 6 months. Still, this is 50% more native storage than
the LTO-2.
2. Overland Storage Neo 2000 with an LTO-2 drive. This is a larger library.
I don't really need 30 media bays, but it could come in handy when I go on
vacation.
My main requirement is reliability. I figured (perhaps falsely) that the
Overland robotics would be superior or more reliable than the Quantum ATL
Superloader. I guess tape drive reliability would be a toss-up since LTO-2
is new, and so will be SDLT 600. I can't find much info on either of these.
Can anyone comment on the reliability of Overland robotics, Quantum
robotics, SDLT drives, or LTO drives?
Finally, I've found usenet to become less and less of a valuable tech
resource. It seems everyone congregates in web based bulletin boards these
days. Anyone know of a good IT admin forum dealing with issues like backups,
file services, Exchange server, etc?
Thanks a lot.


If you want to change technology, check out the Exabyte 110L or 221L LTO
library. Solid equipment, at a good price. Also ask yourself why your M2 is
giving you trouble. If your environment isn't up to the task of feeding the
tape drive at a reasonable rate, then any (S)DLT or LTO tape drive may also
exhibit reliability issues down the road. HP, Seagate and Exabyte all have
excellent whitepapers on optimising backup environments, and what to look
for in case of trouble. You wouldn't be the first to discover that a
workgroupWin2K server with simple backup software can't backup any faster
than 3-6 MB/s...
If your investigations show that your system will not be able to drive the
top-end tape drives properly, you may want to consider Exabyte VXA-2
(80GB@6MB/s native) in an AutoPAK 1x7 desktop loader (costs less than a
stand-alone M2 drive), AutoPAK 1x10 (19" 2U rackmount) or a 430V (max 4
drives, 30 slots).
Rob (who works for Exabyte)

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First of all, if my intent was to give you excuses, then I could have simply
ignored your message and make life easy on myself. I don't get paid to be
present on these newsgroups.
Your message shows exactly why it's important to look at the cause of your
issues. Your description about how moving the drive from one spot to another
changes it's behaviour is a clear sign of electrical trouble. M2 is just as
well shielded as any other decent product in the market, it wouldn't get
accepted by FCC or any OEM if it wasn't. If the drive is in Exabyte's
original external enclosure, it's surrounded by a full steel case, RF
shields included. Your symptoms point to bad grounding, ground loops, faulty
cables, or a bad power supply. Did the drive post an error on it's display,
or did the *software* tell you the drive was bad? More on that later...
Your DLT40 is a perfect match for you 5-8MB/s data rate. It is driven
exactly how it needs to be driven. Your Mammoth2 needs 12-30MB/s and it's
starved for data. Your server isn't bad, your M2 isn't bad, the two are
simply not a good match. Since you mention considering software to increase
throughput, I'd suggest doing that sooner rather than later. When/if you
migrate to another fast technology like SDLT or LTO-1/2, you'll need all the
performance you can squeeze out of your system to keep them running. Make
sure the rest of your environment can actually handle such high speeds.
8MB/s sound pretty much like a maxed-out 100Mb/s Ethernet segment, consider
using a Gigabit trunk if you want to benefit from multiplexed backups. And
be aware that multiplexing increases restore time...
Backup software is a single piece of the entire backup chain. That chain
goes all the way from your client disk, OS and 'client software', through
your network, and then through your backup server OS, drivers, hardware onto
the tape. The software driving it (ArcServe in your case) has the most
powerful interface to you as the user, as it's in your face when you run it.
When a failure of the chain occurs, the software gets to bring the bad news.
It chooses which error to display. When something unexpected occurs, it will
*ALWAYS* point to some other component and blame it for the failure. In your
case, did the M2 drive actually post an error? If so, I'm sure you can send
a diagnostics dump to Exabyte support and have it checked. What associated
error showed up in your server's system event log? The point I'm trying to
make is that your software may not be flawless.
Two weeks ago I spent a week in the lab at Exabyte HQ collecting SCSI bus
traces and logs on a symptom just like the one you describe, but on Netware.
ArcServe loads a tape in the tape drive, rapidly sends out three SCSI Load
commands to which the drive responds it's busy loading the tape, then all
activity on the SCSI bus just stops. The software never checks back if the
drive has completed the load cycle. It just sits there, claiming there's no
tape in the drive. Stopping ArcServe and starting my own diagnostics shows
that the tape is perfectly accessible. Running BackupExec shows it's
perfectly accessible too (with it's own set of idiosyncracies..)
You are not the only one seeing this. Other people are running into the same
issue, also with other technologies like VXA and Sony's AIT. CA sofar has
been a brick wall, they say everything is just fine. They blame Exabyte,
Sony, Adaptec, Novell and their mother-in-law for all failures, but their
software is perfect. They don't want to look at the data we gathered that
shows differently. Only now, after talks on corporate level, are we starting
to make headway on getting this resolved.
Good luck on your next technology choise.
Rob

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