DLT versus 8mm backup

DLT versus 8mm backup

Post by Al Roethlisberg » Sat, 20 Jul 1996 04:00:00



I currently have single 8mm Exabyte tape drives for my backup
solutions.  I am looking at some autoloaders in the near future, and
have been advised not to use the 8mm units, but use DLT instead.

Has anyone had experience with this issue that can offer any advice?

I have received personal opinions from both sales camps but am looking
for industry opinions.

Thanks.

Al Roethlisberger

 
 
 

DLT versus 8mm backup

Post by Greg Linda » Sun, 21 Jul 1996 04:00:00




>I currently have single 8mm Exabyte tape drives for my backup
>solutions.  I am looking at some autoloaders in the near future, and
>have been advised not to use the 8mm units, but use DLT instead.

Here's an opinion: The Exabyte 8500 is one of the most unreliable tape
units I've ever used. The 8505 is a bit better, but both are inferior
to DLT. DLT offers a much higher transfer rate, the media costs more,
and the cartridges are big enough that you may not need an autoloader
for some applications that require an autoloader for the 8505.

I'm sure there are other opinions. :-) Oh, if you want hard numbers, I
think an 8500 survives about 1 year in my experience before the heads
wear through.

-- g

 
 
 

DLT versus 8mm backup

Post by Pascal.Gieng » Sun, 21 Jul 1996 04:00:00


: I currently have single 8mm Exabyte tape drives for my backup
: solutions.  I am looking at some autoloaders in the near future, and
: have been advised not to use the 8mm units, but use DLT instead.
:
: Has anyone had experience with this issue that can offer any advice?
:
: I have received personal opinions from both sales camps but am looking
: for industry opinions.

Don't even play with the idea of buying a DLT drive!
We ordered here a DLT drive 2 months ago. It was a new Quantum drive,
supporting CompacTape IV cartidges (20GB uncompressed). Keep in mind
that these drives have, like DAT and Exabye, a helical scan system
inside. This means they are unreliable like a video cassette recorder.

The first drive being shipped worked 1 week and was not able to reread
older CompacTape III cartridges. So we sent it back to the manufacturer
and got a new one. This one works now... But I can't say how long.
With DAT tapes it is normal here that a recorded DAT type will ne
unreadable after 1 year of storage....

Try to get something from Tandberg. They still use linear recording
style (like a good old tape recorder). There are drives available
now being able to store Gigabytes... ! They are reliable. Very reliable.
Because there's no turning head compartment... (I think they do it
with many thin tracks on the tape, being written simultaneously like
Philips' DCC tape).

(No I don't speak for Tandberg).

Pascal
--

                  WWW  : http://www.geocities.com/WestHollywood/1381/
Das Wort "WINDOWS" stammt aus einem alten Sioux-Dialekt und bedeutet:
"Weisser Mann starrt durch Glasscheibe auf Sanduhr." (gefunden in d.c.t.)

 
 
 

DLT versus 8mm backup

Post by David A. Krau » Sun, 21 Jul 1996 04:00:00



>I currently have single 8mm Exabyte tape drives for my backup
>solutions.  I am looking at some autoloaders in the near future, and
>have been advised not to use the 8mm units, but use DLT instead.
>Has anyone had experience with this issue that can offer any advice?

I've used DLTs in my previous job and will begin installing them on
systems that I currently manage.  I've had tremendous success with
using DLTs.  I've seen backup times decrease to a quarter of the
original time.  Furthermore, DLT tapes are much more dependable.  I've
read that you can perform over 10,000 backups on a single DLT tape
before it should be replaced because of wear-and-tear.  As a real life
testimony, I'm constantly throwing away worn out 8mm tapes, but I've
never thrown away a DLT tape.

The major drawbacks is the upfront investment.  DLT units aren't
cheap; the 20/40gb units that we're purchasing cost around $4000.
Another major investment is in tapes.  The 20/40gb tapes that we
purchased earlier this week were about $100 per tape.

In short, if you require fast and accurate backups, DLT is the best
option.

>I have received personal opinions from both sales camps but am looking
>for industry opinions.
>Thanks.
>Al Roethlisberger


 
 
 

DLT versus 8mm backup

Post by Erwin Fri » Mon, 22 Jul 1996 04:00:00



Quote:

>Don't even play with the idea of buying a DLT drive!
>We ordered here a DLT drive 2 months ago. It was a new Quantum drive,
>supporting CompacTape IV cartidges (20GB uncompressed). Keep in mind
>that these drives have, like DAT and Exabye, a helical scan system
>inside. This means they are unreliable like a video cassette recorder.

This is, of course, pure falsehood.  DLT cartridges use linear formatting.
It's even in the name: Digital LINEAR Tape.

I've experienced both DAT (DDS1 and DDS2), DLT (IIIXT and IV) and
8mm (8505 and 8505XL).  I've had some troubles with the DLT IVs but I'm
told that there was one bad batch produced which caused major grief.

I'm currently using the IIIXT cartridges and I swear by them.  15Gb to
a cartridge (uncompressed) and I can get my whole network backed up in
around six hours or so (for a full backup).

Each DLT is good for 100,000 passes before it needs to be replaced and
should last around 20 years or so before data degradation causes the
media to be faulty.

My predecessor used 8mm tapes to archive certain mission-critical project
directories.  Unfortunately, after a couple of years of sitting on the
shelf these tapes aren't that reliable anymore.  They obey Murphy's law:
the file you need is located on the bad section of tape.

 
 
 

DLT versus 8mm backup

Post by James R. Seama » Mon, 22 Jul 1996 04:00:00




> Newsgroups: comp.unix.admin,comp.unix.misc,comp.unix.questions,comp.unix.solaris

> : I currently have single 8mm Exabyte tape drives for my backup
> : Has anyone had experience with this issue that can offer any advice?

Sorry Pascal,

This information is not correct. The Quantum drives have linear heads.
For detailed information and specs visit the Quantum web site. If memory
is correct the address is www.quantum.com

BTW, we have a model 4700 have had rates as high as 13GB/hour of image
data, which does not  compress well.

jim

> Don't even play with the idea of buying a DLT drive!
> We ordered here a DLT drive 2 months ago. It was a new Quantum drive,
> supporting CompacTape IV cartidges (20GB uncompressed). Keep in mind
> that these drives have, like DAT and Exabye, a helical scan system
> inside. This means they are unreliable like a video cassette recorder.

> Pascal
> --
> Pascal.Gienger    Zentrale Rechner Rechenzentrum Universitaet Konstanz

>                   WWW  : http://www.geocities.com/WestHollywood/1381/
> Das Wort "WINDOWS" stammt aus einem alten Sioux-Dialekt und bedeutet:
> "Weisser Mann starrt durch Glasscheibe auf Sanduhr." (gefunden in d.c.t.)

--

National Library of Medicine - National Institutes of Health
Bldg 38A RM 712     8600 Rockville Pike Bethesda, MD   20894
(voice) 301 435-3145 (fax) 301 402-0118 http://www.nlm.nih.gov
 
 
 

DLT versus 8mm backup

Post by Pascal.Gieng » Mon, 22 Jul 1996 04:00:00



: Sorry Pascal,
:
: This information is not correct. The Quantum drives have linear heads.
: For detailed information and specs visit the Quantum web site. If memory

Okay I admit my error. I was a little bit confused. Thank you for your
information. The problems with our DLT drive are still remaining though...

Pascal
--

                  WWW  : http://www.geocities.com/WestHollywood/1381/
Das Wort "WINDOWS" stammt aus einem alten Sioux-Dialekt und bedeutet:
"Weisser Mann starrt durch Glasscheibe auf Sanduhr." (gefunden in d.c.t.)

 
 
 

DLT versus 8mm backup

Post by Doug Chapm » Tue, 23 Jul 1996 04:00:00




>: I currently have single 8mm Exabyte tape drives for my backup
>: solutions.  I am looking at some autoloaders in the near future, and
>: have been advised not to use the 8mm units, but use DLT instead.
>:
>: Has anyone had experience with this issue that can offer any advice?
>:
>: I have received personal opinions from both sales camps but am looking
>: for industry opinions.
>Don't even play with the idea of buying a DLT drive!
>We ordered here a DLT drive 2 months ago. It was a new Quantum drive,
>supporting CompacTape IV cartidges (20GB uncompressed). Keep in mind
>that these drives have, like DAT and Exabye, a helical scan system
>inside. This means they are unreliable like a video cassette recorder.
>The first drive being shipped worked 1 week and was not able to reread
>older CompacTape III cartridges. So we sent it back to the manufacturer
>and got a new one. This one works now... But I can't say how long.
>With DAT tapes it is normal here that a recorded DAT type will ne
>unreadable after 1 year of storage....

Odd, we have had great luck with our Quantum DLT drives.  The only
problem we had was when we had incorrect data in the /kernel/drv/st.conf
file (solaris).  Once that problem was resolved the drives were
_very_ fast and _very_ reliable (I have never had a tape I couldn't
read).

just my $.02

- Doug

 
 
 

DLT versus 8mm backup

Post by Phillip Faye » Tue, 23 Jul 1996 04:00:00




> : I currently have single 8mm Exabyte tape drives for my backup
> : solutions.  I am looking at some autoloaders in the near future, and
> : have been advised not to use the 8mm units, but use DLT instead.
> :
> : Has anyone had experience with this issue that can offer any advice?
> :
> : I have received personal opinions from both sales camps but am looking
> : for industry opinions.

> Don't even play with the idea of buying a DLT drive!
> We ordered here a DLT drive 2 months ago. It was a new Quantum drive,
> supporting CompacTape IV cartidges (20GB uncompressed). Keep in mind
> that these drives have, like DAT and Exabye, a helical scan system
> inside. This means they are unreliable like a video cassette recorder.

Oops.  DLT stands for Digital Linear Tracking (if I remember right) and
is not a Helical scan system, which is why the tapes are extremely similar
to the old TK tape drives which were standard on DEC Vax.

We have both DLT and Exabyte here.  Our 8505 has given us no problems.  
Our Computing centre recommend replacing the Exabyte drive after 2 or 3
years depending on use because they can get a bit flaky after that.

I would be happy using 8mm for backup but I would use DLT over 8mm for
long term storage.

--
Phillip Fayers, SunAdmin/Support/Programming/Postmaster/Webmaster(TM)
Dept of Physics & Astronomy, University of Wales, College of Cardiff.

 
 
 

DLT versus 8mm backup

Post by Ian G Batt » Tue, 23 Jul 1996 04:00:00




> supporting CompacTape IV cartidges (20GB uncompressed). Keep in mind
> that these drives have, like DAT and Exabye, a helical scan system
> inside. This means they are unreliable like a video cassette recorder.

They don't.  They have serpentine linear tracks --- as in Digital LINEAR
Tape.

Quote:> Because there's no turning head compartment... (I think they do it
> with many thin tracks on the tape, being written simultaneously like
> Philips' DCC tape).

Sort of like DLT, perhaps?

ian

 
 
 

DLT versus 8mm backup

Post by Hans-Peter Sloo » Wed, 24 Jul 1996 04:00:00



>Don't even play with the idea of buying a DLT drive!
>We ordered here a DLT drive 2 months ago. It was a new Quantum drive,
>supporting CompacTape IV cartidges (20GB uncompressed). Keep in mind
>that these drives have, like DAT and Exabye, a helical scan system
>inside. This means they are unreliable like a video cassette recorder.

We have been using two DLT's that are connected to two HP
800's for a couple of month and we have not discoverd any
problems with them until now. We got them from DEC. They have
two types with different firmware. One type is for DEC
equipment and the other type is for non DEC equipment.

--------------------------------------------------------------
-----------
Hans-Peter Sloot Phone:+31 50 5855436   E

DISCLAIMER: This statement is not an official statement from,
nor does
it represent an official position of, PTT Telecom BV.
--------------------------------------------------------------
-----------

 
 
 

DLT versus 8mm backup

Post by Ger Timme » Wed, 24 Jul 1996 04:00:00




>>Don't even play with the idea of buying a DLT drive!
>>We ordered here a DLT drive 2 months ago. It was a new Quantum drive,
>>supporting CompacTape IV cartidges (20GB uncompressed). Keep in mind
>>that these drives have, like DAT and Exabye, a helical scan system
>>inside. This means they are unreliable like a video cassette recorder.

>We have been using two DLT's that are connected to two HP
>800's for a couple of month and we have not discoverd any
>problems with them until now. We got them from DEC. They have
>two types with different firmware. One type is for DEC
>equipment and the other type is for non DEC equipment.

We got a DEC TZ87N DLT drive. When I connect it to a Solaris 2.5 system
it works fine, however on Solaris 2.4 I get the following warnings:

WARNING: hardware_address: write: not modulo 8192 block size

(were hardware address is something like:

I've the same /kernel/drv/st.conf on 2.4 as on the 2.5 system.

Any pointers?

Thanks in advance,

      Ger
--
     ____/                Ger Timmens, CI&A - AZU, Heidelberglaan 100,
    /      ___/  _ \     3584 CX Utrecht, The Netherlands.

 _____/  ___/ _/ _\    phone: +31-30-(2)508488, fax: +31-30-(2)542028

 
 
 

DLT versus 8mm backup

Post by Matthew Sa » Wed, 24 Jul 1996 04:00:00



>should last around 20 years or so before data degradation causes the
>media to be faulty.

Hrmm. DLT not having been around for 20 years or so, how do you know?
Even if the media is fine for 20 years, that doesn't mean my data is.
Ever hear of emf or cosmic rays?

Quote:>My predecessor used 8mm tapes to archive certain mission-critical project
>directories.  Unfortunately, after a couple of years of sitting on the
>shelf these tapes aren't that reliable anymore.  

If it's that mission critical, don't use magnetic media. I'm not
trying to single out DLT rather, the inherent danger of magnetic
media for long term archival.

-Matthew

----------------------------------------------------------------------------
Matthew Sams                  | All this talk about everyone being connected
Systems Programmer            | to the Internet by the year xxxx ignores the
School of Computer Science    | simple fact that a large number of people in
McGill University             | the world are fighting for survival.
----------------------------------------------------------------------------

 
 
 

DLT versus 8mm backup

Post by R.Whittingto » Thu, 25 Jul 1996 04:00:00



> Each DLT is good for 100,000 passes before it needs to be replaced and
> should last around 20 years or so before data degradation causes the
> media to be faulty.

Can you cite the source for these figures please? Which tape/drive
combination achieves this? Is this your experience?

thanks,
royd.

--
Royd Whittington      | Tel: (+44) (0)1925 603226
Daresbury Laboratory  | FAX: (+44) (0)1925 603230

Cheshire WA4 4AD UK   | Department for Computation and Information

 
 
 

DLT versus 8mm backup

Post by Al Slat » Tue, 30 Jul 1996 04:00:00



: We got a DEC TZ87N DLT drive. When I connect it to a Solaris 2.5 system
: it works fine, however on Solaris 2.4 I get the following warnings:

: WARNING: hardware_address: write: not modulo 8192 block size

: (were hardware address is something like:

: I've the same /kernel/drv/st.conf on 2.4 as on the 2.5 system.

: Any pointers?

Yep. /kernel/drv/st.conf, entry for the drive properties, third number
along -- it's the blocksize, 0 for variable or fixed size. If you have
an app that writes out data in blocksizes not precisely a multiple of
this value (if it's not 0 for variable) then you get the above message
on console. Your third value in the config line is set to 8192 by the
looks of it... You could find out what's upsetting it by using truss...

cheers,
al
(not speaking for HP..)

 
 
 

1. DLT/8mm backup solutions

Does anyone have any experiences with performing backups on Sun's
DLT4000 and 20-40GB 8mm tape drives?  In particular, I would like to
find out the following:

1) what kind of speed improvements are there over conventional 8mm tape
drives?

2) how reliable are these drives, e.g. MTBF, head-life.

3) what is the life-time of DLT tapes compared to 8mm tapes.

Any comments are welcome and appreciated.

Shawn

2. Solaris 2.6 sys req????!!!!!

3. AHA2940U timeout

4. Replacement of Xterms

5. Linux and IDE/SCSI Drives / 8mm Backup / Irwin Backup / Digiboar

6. SEGV in NFS in deep directory (was: bash: looping over all files in directory)

7. 8mm vs DLT?

8. DLT vs. 8mm Storage Media for E6500?

9. copying a DLT tape to 8mm

10. DLT vs 8mm

11. Read 8mm backups