9 May
2007
9 May
'07
4:48 a.m.
On Tue, 8 May 2007, Dave McGuire wrote:
On May 8, 2007, at 8:40 PM, Zane H. Healy wrote:
Personally I'd rate it a bit different.
DLT > 4mm DAT > QIC > 8mm
My ordering would be:
DLT > QIC > 4mm DAT > 8mm
In my experience, both 4mm and 8mm are "write-only backups". I shy away
from any helical-scan media at this point. DLT is rock-solid and I trust my
most critical stuff to it every day. It's hard to believe that it grew out
of the abominable TK-50!
Amen. My experiences with 4 & 8mm rotary-head units have been abysmal.
The Exabyte drives, in particular, just seem to randomly drop dead without
warning. And, as others comment, the 1/2-ht. front-loading Exabyte drives
are a mechanical nightmare. They make the worst 80s vintage VCR load
mechanism look downright simple to repair.
The majority of my backups are made on DLT IV tapes using DLT7000 series
drives (mostly Compaq and HP OEM units). If you have the latest firmware
flashed, they are incredibly solid. In some cases, used tapes require a
heroic amount of bulk erasing before they can be reliably written. I have
heard this is a result of them being previously used on lower-density
drives, but have no proof of this. One of the coolest features of DLT is
that they are self-aligning. The drive goes through an intricate dance
during tape load to teach the head servo where each track center is. I
believe they are capable of re-training during operation if things are
found to drift.
Also, someone in this thread mentioned that DLT IV was not a
read-after-write medium. Is that really the case? I have seen drives
throw errors when trying to write damaged media. If they don't do a
read-back, how would they know?
Another personal favorite is the late Onstream linear tape drive. I have
an ADR2 120GB external SCSI drive that just keeps on ticking. Media is
getting tough to find, but occasionally I score a few cartridges on ebay.
For reasons unknown, the 1/2 size 60GB ADR cartridges do not work at all
in these drives. The 120s have never given a problem. These units do not
seem to perform a read-after-write, but I've gotten in the habit of making
a second verification pass on the tape before considering a backup
complete.
Steve
--
8 mm wasn't bad. At about that time, we were
heavily involved in
specifying tape for customers and we tended to rank things this way:
DLT > 8mm > 4mm DAT > Travan > QIC.
Interesting. That's about my assessment too, though I don't use tapes
all that much.