SUMMARY: which tape drive, please...

From: Chris Wozniak (
Date: Mon May 13 1996 - 17:20:00 CDT

Estimed Mangers

Here's the summary:

 I received 13 answers to my query. The overwhelming majority (9) were
 in favor of DLTs, only one respondent preferred Mammoth and mainly because
 of the Exabyte domination of the market and backward compatibility.
 The prize for the best answer goes to Rob Worsham for his
 excellent list of pros and cons.
 I apologise for spreading the misleading info about pricing of DLT
 and Mammoth tapes. I sourced both since and the prices in Australian dollars
 are $215/DLT and $195/Mammoth. Why are they so expensive, when according to
 the current exchange rate ($1Au=0.80$US) and the prices quoted by
 US respondents they should cost about $115 Aus will probably remain one of
 the dark secrets of the Universe.

 Disk quotas, suggested by Dave Cain are unfortunately impossible to
 implement here because of the apps software requirements.

 I'll certainly test the disk transfer speed, as suggested by Dave Mitchell,
 I sort of always took this to be much more than tape and I wasn't lateral
 enough to think of such a test.

 Warm thanks to all who replied

 Chris Wozniak

The query:

 Greetings o gurus.
 I look after 17 Suns (SunOS and Solaris) with a large file server, etc.
 Recently our disk space has increased dramatically (good news), but
 the users gobble it up with an amazing speed (bad news) and the backups
 take forever (worse news). Currently used 2 stackers with Exabyte drives
 inside can't cope with 120 Gb. The big question is which way to go:
 Exabyte Mammoth or DLT. I would greatly appreciate any comments on this
 subject, particularly about Sun repackaged Quantum DLTs 4700, that the
 local Sun rep waxes lyrical about, and the Mammoths. I've read the recent
 Summary about the latter, but it is somewhat inconclusive.
 Another factor is that DLT tapes retail here for about $A 200, 7 times
 more than Exabytes!!!!
 Will gladly summarize.
 Thanks in advance
 Chris Wozniak
 System Amdinistrator
 WAPET ph +61 9 263 6398 e-mail

From: (Bruce Cheng)

For the capacity you need, you can either go for a 40-80 tape library (8mm)
(non-mamooth) or a DLT tape. In long run the DLT tapes are the way to go.
(only if the media cost can go down a bit)

I have an EXB440 (XL capacity but I use only 112m 5GIG).

Just ordered a DLT4700 from Sun also.


From: (Robert D. Worsham)


  We're currently going through the same process, and I'm leaning toward
  the DLT's with the following reasons:

      1) Capacity: Mammoth will equal DLT4000 capacity, but the
                         new DLT7000 are due out in the next month or
                         so with 70 Gb capacity per tape....
                         Advantage: DLT

      2) Reliability: a) Mammoth is still Helical-scan, and therefore
                            the tape has contact with the tape head ==>
                            tape heads will wear....
                         b) In DLT's the tape head's don't contact the
                            tape ==> no tape head wear..
                         I'm assuming the other mechanical components
                         have similar reliability.
                         Advantage: DLT

       3) Speed: Both the DLT7000 and the Exabyte Mammoth seem
                         to have similar IO speeds (at least on paper)
                         Advantage: none

       4) Cost: a) to purchase: DLT7000 are ~US$7K
                                         Exabyte Mammoth are ~US$5K
                         b) to own: DLT tapes are ~US$100 each
                                         Mammoth tapes are projected
                                         ~US$95 each
                         Advantage: none

       5) Compatibility: Exabyte Mammoth will read my old 8mm tapes.
                         DLT will not.
                         Advantage: Mammoth

   Conclusions: DLT seems to have some advantages over Mammoth...

> particularly about Sun repackaged Quantum DLTs 4700, that the
> local Sun rep waxes lyrical about,

  I'm not familliar with Sun's offering, but I assume that it's based
  on the DLT4000.

  You haven't priced Mammoth tapes (See Above) ...

  Hope this helps,

  -- Bob

From: Brad Young <>

  We use DLTs here. Formerly we used Exabytes. DLTs are more reliable and
quicker. I haven't tried the Mammoth, but has it actually been released?
It had been promised for the past three years....
  $200 for DLT tapes!!?? We are in the wrong business.... ;->


From: Dave Cain <>

Aside from your other problems, I would think about enacting
file system quotas for the long term. When users know they
have a limited amount of space, they are more likely to remove
unneeded stuff before they both to complain about needing
a larger quota. This should help get your disk growth under

From: (Dan A. Zambon)

'Morning, Chris....
I am a manager of a lab that contains a lot of suns as well. We
currently use two backup tape drives, both from MTI. One is a 7
tape, gravity-fed 75GB system. The other is a 10 tape robotic arm
100GB system. Scripts are used to do the actual backups. They run
day and night.

I also am looking into better backup solutions. I have had one
of my guys looking into the Mammoth drives you mentioned from
Exabyte. The following is general info on the drives:

Available now with 90 day delivery...

        Comes in 16 configurations, options include

        SCSI - Fast, Wide or Fast, Narrow
             - Single Ended or Diff.

        Mounting - Internal or External

        Display - Standard LEDs or New LCD Display

        Cost - Approx 6k

        Software Drivers - Solaris 2.5 OK, 2.4 Not Ready

        Media, Made by Sony for Exabyte -Two Sizes

                Short Tape - $36 each

                Long Tape - $96 each

                Long tape holds 20 GB Native, don't
                know capacity of short tape..

The items that jump out at me are the Solaris 2.5 restriction
(not really a problem for us, as our environment is now approximately
50% Solaris 2.5 and growing) and the COST OF THE FLIPPIN' TAPES!
My guess is they are made of gold, and come with an attractive
attendent whose main job is to swap the tapes for you.......opse,
I digress.......:>)


From: (Patrick O'Brien)

Hi, Chris

I had to face the same decisions when our systems went from ~100GB to
~400GB. What I do know is that the DLT stackers are problematic, but
the single DLT's (4000)'s are wonderful. The technology has the
tape floating over the heads as opposed to coming in contact as
the Exabytes do. I went with the DLT's because I've just had it
with helical scan technology.


From: Darren King <>

Nothing is faster than DLT, Chris. If you can afford it, go for it.

Darren King, Legato Systems, Canada

From: (Jeff Wasilko)

Yes, the tapes are more expensive (for the DLT COmpactTape 4),
but you get a more reliable, faster media.

On a recent test from a filesystem with a fair number of small,
non-compressible files (images), I saw nearly 1500 k/s writing to
a model 4 tape, and around 1200k/s writing to a model 3 tape
(lower density). The max speed for a DLT 4 is 3000 k/s.

This was on a Sparc 20 running Solaris 2.4, and using the
internal SCSI bus for the drive and an external fas/wide
connection to a RAID.


Jeff Wasilko, Systems Representative       Autologic Information International
Pager: +1 800 605 5679

------------------------------------------------------------------------------ From: Nate Itkin <>

I currently back-up 704 GB. My DLT-2000 reliability and performance has been outstanding.

Although the price of the h/w and media is attractive, I find the reliability of the Exabyte 8500C series to be unacceptable for the size of my data set.

Haven't tried the Mammoth drives - perhaps reliability has improved.

Haven't tried the DLT-4000 series. The optimal approach might be to put DLT-2000 on-line to solve your immediate back-up problem and upgrade later when the media cost comes down.

A final thought. Don't forget to consider media reuse and shelf life in your cost comparison. The DLT tapes are good for significantly more read/write passes than Exabyte (even if you use worst case DLT numbers and best case Exabyte numbers).

*** Official Disclaimer

My opinion ONLY - NOT the position of Intel corporation (they ignore my ideas and opinions - maybe you should to).


-- - Nate Itkin - Portland Technology Development, Intel Corporation Aloha, Oregon - E-mail:

------------------------------------------------------------------------------ From: Salvatore Saieva <>


I priced the 20GB tapes for Mammoth at about US $100. So they are equally expensive.

My opinion on the 8mm vs DLT choice is to go with the format that is more prevalent. For instance, I don't expect vendors to ship software on DLT. (In another few years I don't exepect software to be shipped on any tape media, but that's another discussion.) Also, for me, I have been using 8mm for 6 years now, hence, I have a lot of 8mm tapes in my archive that I still need to support.

Since the Mammoth is doing 20GB now (40 compressed), which equals DLT in capacity, and the Mammoth has better transfer rates (3MB/sec, on paper) I don't see the sense in DLT. Exabyte has also said they see the Mammoth technology scaling to the 150GB range, so it seems like there is plenty room to grow.

Sal. --- Salvatore Saieva PRINCIPIA Partners LLC E-Mail: Harborside Financial Center Phone: (201) 946-0300 902 Plaza II, 9th Floor Fax: (201) 946-0320 Jersey City, NJ 07311

Exhortation: ``Aesthetics are more important than efficiency.'' -DEK

------------------------------------------------------------------------------ From: Dave Mitchell <>

I cant provide any direct opionions, but one thing to bear in mind is to determine the limiting factor in backup speed. Some tape drives are capable of higher speeds than the disks they are supposed to be backing up! In this case, it may be better going for many cheap but slow tape drives, rather than a few fast expensive ones.

Try backing up to /dev/null, and seeing how long it takes. This will give you an upper bound on dump performance. There's no benefit in geting a tape drive faster than this. For example, in my simple setup (no disksuite stuff like striping), a dump to /dev/null goes about 600Kb/s. So we use DDS2 DATs - we have 5 drives, so lots of disks on diffeent machines can be backed up simultaneously.

Of course, I may be teaching my Grandmother to suck eggs here....


* David Mitchell, Systems Administrator, email: * Dept. Computer Science, Sheffield Uni. phone: +44 114-282-5573 * 211 Portobello St, Sheffield S1 4DP, UK. fax: +44 114-278-0972 * * Standards (n). Battle insignia or tribal totems * * >>>> Support Randal Schwartz! email for info <<<<<

------------------------------------------------------------------------------ From: (Andrew Foote)

I understand there's a new DLT (7000 ??) that has a capacity of 70 GB (assuming 2:1 compression) and a data xfer rate of 6 MBs.

I would caution a little re Mammoth - I've been promised "delivery is imminent" for over 2 years !! Are they really shipping now ?? Availability ??

DLT from my experience has been faultlesss. A White paper on such indicated a capacity of 200 GB (!!) per cartridge was expected toward the end of the decade.

Hope this helps ...

Andrew Foote

------------------------------------------------------------------------------ From: (Rico Jansen)

In article <>, you wrote: >local Sun rep waxes lyrical about, and the Mammoths. I've read the recent >Summary about the latter, but it is somewhat inconclusive. >Another factor is that DLT tapes retail here for about $A 200, 7 times

I am using a DLT unit, not one from Sun. But a 10Gig none the less. The newer ones are 20Gig (all uncompressed figures). I am very happy with it since it is quite fast, easily 1M/sec when backuping. I have no experience with the stacker. However $A 200 for tapes seems steep, but I suspect that it is a 7 pack of tapes. Since that's what I bought when the drive was purchased.

GrtX. Rico -- Rico Jansen ( VPRO Java GCS d+(-) H s+ !g p1 !au a- w+ v(-) C++ USL++++$ P L++ 3 E- N++ K++ W---(--) 2.1 M(-) V- po Y+ t+ !5 !j R !G tv- b+++ D B- e++ u*+ h f r-- (!)n+ y*+

Status: RO

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