Tapes not achieving anywhere near capacity

I'm using BENT 7.3, and using an ADIC Scalar 458 that has 4 DLT 8000 drives
w/ 40/80 gb storage capacity and a 48 tape lib to choose from. We are using
hardware compression, and the drive firmware is 022B. However, Our tapes
are getting nowhere near capacity before our tapes will simply not be written
to anymore. I have some that will get 30 or 40 gb, but some that get as
little as 9.72mb, or 2 gb.(No joke). They're not being marked as bad by
BE either, so that shouldn't be an issue. Does anyone have any ideas on
what we can do to get better storage capacity on our tapes? Even 60gb would
fine... anything more than 30/40. Thanks in advance for any help!
-LC

If you re-label one of the tapes (equvalent to a quick-erase) and try a
backup, how much gets written to the tape?

Larry wrote:[color=blue]
>
> I'm using BENT 7.3, and using an ADIC Scalar 458 that has 4 DLT 8000 drives
> w/ 40/80 gb storage capacity and a 48 tape lib to choose from. We are using
> hardware compression, and the drive firmware is 022B. However, Our tapes
> are getting nowhere near capacity before our tapes will simply not be written
> to anymore. I have some that will get 30 or 40 gb, but some that get as
> little as 9.72mb, or 2 gb.(No joke). They're not being marked as bad by
> BE either, so that shouldn't be an issue. Does anyone have any ideas on
> what we can do to get better storage capacity on our tapes? Even 60gb would
> fine... anything more than 30/40. Thanks in advance for any help!
> -LC[/color]

If your throughput is slow you are going to lose tape capacity. You can
listen
to the drive - if you hear it starting and stopping instead of streaming
tape continuously
you are losing capacity to the interrecord gaps the drive has to create.

When I could stream data at 7 MBytes/sec into a DLT 7000 I've gotten as
much as 111 GB on one tape
(with Veritas Netbackup or Legato Networker).

BENT's network agents are terribly slow - we get only about 40 or 50
GB per tape at
a throughput of 1.2 Mbytes/sec. I've analyzed it to heck and gone and
BENT is definitely the bottleneck,
and Veritas Support themselves said I should not expect 100Mbit wire
speeds from BENT.

I have no idea what would cause you to get only a few MB on a DLT, other
than bad media.
Perhaps BENT is not reporting the error correctly/

-wsanders

Don't know why Veritas would say that.

I've seen speeds in the 350/400MB/min range for network backups on fast
servers over 100MB full duplex network. And my average is between
200-250 MB/min.

If you are seeing speeds that low, verify that AUTONEGOTIATE is turned
OFF on all switch ports and NICs. Hard set each end of every pipe the
backup will go through.

Wiley Sanders wrote:[color=blue]
>
> If your throughput is slow you are going to lose tape capacity. You can
> listen
> to the drive - if you hear it starting and stopping instead of streaming
> tape continuously
> you are losing capacity to the interrecord gaps the drive has to create.
>
> When I could stream data at 7 MBytes/sec into a DLT 7000 I've gotten as
> much as 111 GB on one tape
> (with Veritas Netbackup or Legato Networker).
>
> BENT's network agents are terribly slow - we get only about 40 or 50
> GB per tape at
> a throughput of 1.2 Mbytes/sec. I've analyzed it to heck and gone and
> BENT is definitely the bottleneck,
> and Veritas Support themselves said I should not expect 100Mbit wire
> speeds from BENT.
>
> I have no idea what would cause you to get only a few MB on a DLT, other
> than bad media.
> Perhaps BENT is not reporting the error correctly/
>
> -wsanders[/color]

PLEASE.....substanciate this CLAIM!
......with a link or anything you like
...OR dont make such such a rubbish statement.

Thank you!!

jk


"Wiley Sanders" <wsanders@wsanders.net> wrote in message
news:3A27E5EB.B09932C7@wsanders.net...[color=blue]
> If your throughput is slow you are going to lose tape capacity. You can
> listen to the drive - if you hear it starting and stopping instead of[/color]
streaming[color=blue]
> tape continuously
> you are losing capacity to the interrecord gaps the drive has to create.[/color]

I'm using BENT 8.5 with Sony DAT SDT-10000 (20/40gb) and have the same problem
with DDS-4 tapes. I can't get more than 10gb on a native 20gb tape, while
I can with DDS-3 tapes (12/24gb).
Do you see an error message like:

***The tape drive is having problems writing data. No data has been lost,
but there has been a reduction in the capacity of the tape***


"Larry" <chisholm-larry@DOL.gov> wrote:[color=blue]
>
>I'm using BENT 7.3, and using an ADIC Scalar 458 that has 4 DLT 8000 drives
>w/ 40/80 gb storage capacity and a 48 tape lib to choose from. We are using
>hardware compression, and the drive firmware is 022B. However, Our tapes
>are getting nowhere near capacity before our tapes will simply not be written
>to anymore. I have some that will get 30 or 40 gb, but some that get as
>little as 9.72mb, or 2 gb.(No joke). They're not being marked as bad by
>BE either, so that shouldn't be an issue. Does anyone have any ideas on
>what we can do to get better storage capacity on our tapes? Even 60gb would
>fine... anything more than 30/40. Thanks in advance for any help!
>-LC[/color]

I would start by checking to see if compression is enabled on the drive and
in the software. Next, I have never ever seen 2:1 compression. I use
Backup Exec for Win2K Server 8.5 with the latest service pack for 8.5. In
all my years of using both Backup Exec and ArcserveIT, I have never had
better than 1.6 : 1 compression. Usually it is 1.3 :1. Which would mean
the 20/40 tape would never get more than 26-32 GB before it was filled. I
have the HP DAT40i OBDR drive installed at home. I use Win2K Server Edition
for software level RAID on my SCSI drives. I have tried both hardware and
software compression. I found that software compression is faster and does
the same job as hardware compression. Most of the files I am backing up
are already compressed: Games, pictures, etc. You will not get any more
compression on these files. I would check you backup job properties to see
if compression is turned on. You need to verify that the tape backup unit
is set for hardware compression enabled in the device manager and your
backup job properties has compression enabled. I suggested that you try
software compression and see how it works compared to hardware compression.

"Frank van Poelje" <frankvp@ecomare.nl> wrote in message
news:3adc3bc4$1@hronntp01....[color=blue]
>
> I'm using BENT 8.5 with Sony DAT SDT-10000 (20/40gb) and have the same[/color]
problem[color=blue]
> with DDS-4 tapes. I can't get more than 10gb on a native 20gb tape, while
> I can with DDS-3 tapes (12/24gb).
> Do you see an error message like:
>
> ***The tape drive is having problems writing data. No data has been lost,
> but there has been a reduction in the capacity of the tape***
>
>
> "Larry" <chisholm-larry@DOL.gov> wrote:[color=green]
> >
> >I'm using BENT 7.3, and using an ADIC Scalar 458 that has 4 DLT 8000[/color][/color]
drives[color=blue][color=green]
> >w/ 40/80 gb storage capacity and a 48 tape lib to choose from. We are[/color][/color]
using[color=blue][color=green]
> >hardware compression, and the drive firmware is 022B. However, Our[/color][/color]
tapes[color=blue][color=green]
> >are getting nowhere near capacity before our tapes will simply not be[/color][/color]
written[color=blue][color=green]
> >to anymore. I have some that will get 30 or 40 gb, but some that get as
> >little as 9.72mb, or 2 gb.(No joke). They're not being marked as bad by
> >BE either, so that shouldn't be an issue. Does anyone have any ideas on
> >what we can do to get better storage capacity on our tapes? Even 60gb[/color][/color]
would[color=blue][color=green]
> >fine... anything more than 30/40. Thanks in advance for any help!
> >-LC[/color]
>[/color]