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| Author |
Message |
Larry Hodges
Guest
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 Posted: Mon Aug 28, 2006 12:15 am Post subject: DDS4 - hardware compression not working |
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There is no ng for backup or DAT, so I guess I'll ask this here.
I have a DDS-4 Seagate 40 (also called an Archive Python), model
STD62401LW-S. It's 20gb native, 40 gb compressed. However, apparently
compression isn't working. I conclude that because at 20gb into the backup,
I'm prompted for a 2nd tape. I'm using NTBackup, the built-in backup app
with x64. I've tried it with and without software compression enabled.
OS is XP x64. Controller is Adaptec 39320a. Tape is on channel A with two
other HDDs. RAID is on channel B.
I just flashed the ROM, so it's current. Driver is current. According to
Device Manager, compression is enabled for the drive. Any ideas?
Thanks,
-Larry |
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Folkert Rienstra
Guest
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| Posted: Mon Aug 28, 2006 12:15 am Post subject: Re: DDS4 - hardware compression not working |
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"Larry Hodges" <2larry2@2maximizesoftware2.com> wrote in message news:BOKdnZ1x6MZwNm_ZnZ2dnUVZ_vGdnZ2d@comcast.com
| Quote: | "Michael Baeuerle" <michael.baeuerle@stz-e.de> wrote in message news:gnhas3-4vl.ln1@micha.freeshell.org...
Larry Hodges wrote:
I have a DDS-4 Seagate 40 (also called an Archive Python), model
STD62401LW-S. It's 20gb native, 40 gb compressed. However, apparently
compression isn't working. I conclude that because at 20gb into the backup,
I'm prompted for a 2nd tape. I'm using NTBackup, the built-in backup app
with x64. I've tried it with and without software compression enabled.
What data are you writing on the tape? Some types of data like audio or
video cannot be compressed at all or at very bad ratios by the lossless
compression algorithm used in DDS drives.
Micha
Maybe half of the data are JPGs. The rest, website backups, database apps,
installation packages, deployment packages, programming projects, Word and
Excel docs, etc.
I've run a test application that says compression is working properly.
However, I'll go to do a backup. The pre-compressed calculations will say 26gb.
In my way of thinking,
|
Which is?
| Quote: | that should fit on a 40gb compressed tape.
|
And why is that, in the absence of a 'compressed calculation'?
What are the prerequisites for getting 40GB on such tape?
I'll bet it is maximum compressible data and full uninterrupted streaming.
So how do you insure the streaming part?
| Quote: | It doesn't. I tried StompSoft's BackupMyPC tonight with the same results.
That's a nice application btw. The only non-enterprise level backup app
that backs up open files. Only about $40 too. Also works great on x64.
Roxio doesn't.
Any other ideas?
|
Make an image backup?
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Michael Baeuerle
Guest
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| Posted: Mon Aug 28, 2006 12:14 pm Post subject: Re: DDS4 - hardware compression not working |
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Larry Hodges wrote:
| Quote: |
I have a DDS-4 Seagate 40 (also called an Archive Python), model
STD62401LW-S. It's 20gb native, 40 gb compressed. However, apparently
compression isn't working. I conclude that because at 20gb into the backup,
I'm prompted for a 2nd tape. I'm using NTBackup, the built-in backup app
with x64. I've tried it with and without software compression enabled.
|
What data are you writing on the tape? Some types of data like audio or
video cannot be compressed at all or at very bad ratios by the lossless
compression algorithm used in DDS drives.
Micha |
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Larry Hodges
Guest
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| Posted: Mon Aug 28, 2006 1:40 pm Post subject: Re: DDS4 - hardware compression not working |
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"Michael Baeuerle" <michael.baeuerle@stz-e.de> wrote in message
news:gnhas3-4vl.ln1@micha.freeshell.org...
| Quote: | Larry Hodges wrote:
I have a DDS-4 Seagate 40 (also called an Archive Python), model
STD62401LW-S. It's 20gb native, 40 gb compressed. However, apparently
compression isn't working. I conclude that because at 20gb into the
backup,
I'm prompted for a 2nd tape. I'm using NTBackup, the built-in backup app
with x64. I've tried it with and without software compression enabled.
What data are you writing on the tape? Some types of data like audio or
video cannot be compressed at all or at very bad ratios by the lossless
compression algorithm used in DDS drives.
Micha
|
Maybe half of the data are JPGs. The rest, website backups, database apps,
installation packages, deployment packages, programming projects, Word and
Excel docs, etc.
I've run a test application that says compression is working properly.
However, I'll go to do a backup. The pre-compressed calculations will say
26gb. In my way of thinking, that should fit on a 40gb compressed tape. It
doesn't. I tried StompSoft's BackupMyPC tonight with the same results.
That's a nice application btw. The only non-enterprise level backup app
that backs up open files. Only about $40 too. Also works great on x64.
Roxio doesn't.
Any other ideas?
-Larry |
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Mike Tomlinson
Guest
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| Posted: Mon Aug 28, 2006 1:51 pm Post subject: Re: DDS4 - hardware compression not working |
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In article <BOKdnZ1x6MZwNm_ZnZ2dnUVZ_vGdnZ2d@comcast.com>, Larry Hodges
<2larry2@2maximizesoftware2.com> writes
| Quote: | I'm prompted for a 2nd tape. I'm using NTBackup, the built-in backup app
with x64. I've tried it with and without software compression enabled.
|
That suggests to me that the drive cannot further compress the data it's
being sent.
| Quote: | Maybe half of the data are JPGs.
|
JPGs are already compressed. Trying to compress already-compressed data
usually only makes it larger. This could be why the tape is filling up;
the fact that it fills up at or about its uncompressed capacity is a
coincidence.
--
(\__/)
(='.'=) This is Bunny. Copy and paste Bunny into your
(")_(") signature to help him gain world domination.
http://www.thisisbunny.com/ |
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Larry Hodges
Guest
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| Posted: Mon Aug 28, 2006 10:12 pm Post subject: Re: DDS4 - hardware compression not working |
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"Mike Tomlinson" <mike@NOSPAM.jasper.org.uk> wrote in message
news:Sst3PMCs6q8EFwrg@jasper.org.uk...
| Quote: | In article <BOKdnZ1x6MZwNm_ZnZ2dnUVZ_vGdnZ2d@comcast.com>, Larry Hodges
2larry2@2maximizesoftware2.com> writes
I'm prompted for a 2nd tape. I'm using NTBackup, the built-in backup
app
with x64. I've tried it with and without software compression enabled.
That suggests to me that the drive cannot further compress the data it's
being sent.
Maybe half of the data are JPGs.
JPGs are already compressed. Trying to compress already-compressed data
usually only makes it larger. This could be why the tape is filling up;
the fact that it fills up at or about its uncompressed capacity is a
coincidence.
|
I thought that might be the case also. So last night I selected various
folders, all containing just data and program files, and the same thing.
Using software compression, I was able to get 26gb on a tape. But with
hardware compression, they recommend you not use software compression.
Obviously, this issue doesn't belong on the SCSI ng. I couldn't find
another group specific to my issue, and since I hang out here, I thought I'd
ask. Sorry guys.
Problem is, I bought the drive used. In addition, Seagate no longer
supports these drives, but rather Quantum. However, the drive is still
current and can be purchased new. I've emailed Quantum. I'll see what they
say.
-Larry |
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Steve Cousins
Guest
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| Posted: Tue Aug 29, 2006 12:24 am Post subject: Re: DDS4 - hardware compression not working |
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Larry Hodges wrote:
| Quote: | "Mike Tomlinson" <mike@NOSPAM.jasper.org.uk> wrote in message
JPGs are already compressed. Trying to compress already-compressed data
usually only makes it larger. This could be why the tape is filling up;
the fact that it fills up at or about its uncompressed capacity is a
coincidence.
I thought that might be the case also. So last night I selected various
folders, all containing just data and program files, and the same thing.
Using software compression, I was able to get 26gb on a tape. But with
hardware compression, they recommend you not use software compression.
|
I've found that hardware compression is not is good as software
compression (my comparisons were with DLT/SDLT vs. gzip). So, in your
test, hardware compression may still be "working" but it may not look
like it is. You should test it with something really compressable like
text files or postscript files. Make a directory of a few large
PostScript files and then keep on copying them recursively into new
folders, doubling your the space used each time you copy. It shouldn't
take _too_ long to get 30 GB say. This should easily fit on a 20GB tape
with any sort of standard compression. It would be a lot easier in
Linux using dd or a short script. |
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Jeremy Boden
Guest
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| Posted: Tue Aug 29, 2006 12:24 am Post subject: Re: DDS4 - hardware compression not working |
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On Mon, 2006-08-28 at 10:12 -0700, Larry Hodges wrote:
| Quote: | "Mike Tomlinson" <mike@NOSPAM.jasper.org.uk> wrote in message
news:Sst3PMCs6q8EFwrg@jasper.org.uk...
In article <BOKdnZ1x6MZwNm_ZnZ2dnUVZ_vGdnZ2d@comcast.com>, Larry Hodges
2larry2@2maximizesoftware2.com> writes
I'm prompted for a 2nd tape. I'm using NTBackup, the built-in backup
app
with x64. I've tried it with and without software compression enabled.
That suggests to me that the drive cannot further compress the data it's
being sent.
Maybe half of the data are JPGs.
JPGs are already compressed. Trying to compress already-compressed data
usually only makes it larger. This could be why the tape is filling up;
the fact that it fills up at or about its uncompressed capacity is a
coincidence.
I thought that might be the case also. So last night I selected various
folders, all containing just data and program files, and the same thing.
Using software compression, I was able to get 26gb on a tape. But with
hardware compression, they recommend you not use software compression.
.... |
Obviously the hardware compression can't compress something that's
already been compressed by software (otherwise the software could be
re-written to make a better job of compression...).
Treat jpg and exe files as not worth compressing, database as fairly
compressible (usually). Note that it is usual to quote a 2x factor for
compression - even though you will need some very special data to
achieve this!
Is there any reason why you should not use a second tape?
How about using an incremental backup strategy?
--
Jeremy Boden |
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Mike Tomlinson
Guest
|
| Posted: Tue Aug 29, 2006 12:24 am Post subject: Re: DDS4 - hardware compression not working |
|
|
In article <Y_CdnUC31p9ivm7ZnZ2dnUVZ_rydnZ2d@comcast.com>, Larry Hodges
<2larry2@2maximizesoftware2.com> writes
| Quote: | But with
hardware compression, they recommend you not use software compression.
|
Agreed.
| Quote: | Obviously, this issue doesn't belong on the SCSI ng.
|
I don't see that it's a problem posted here.
| Quote: | Problem is, I bought the drive used. In addition, Seagate no longer
supports these drives, but rather Quantum. However, the drive is still
current and can be purchased new. I've emailed Quantum. I'll see what they
say.
|
One last thought - have you checked the DIP switches on the drive?
Usually, one of those is to enable/disable hardware compression.
--
(\__/)
(='.'=) This is Bunny. Copy and paste Bunny into your
(")_(") signature to help him gain world domination.
http://www.thisisbunny.com/ |
|
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|
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Larry Hodges
Guest
|
| Posted: Tue Aug 29, 2006 12:24 am Post subject: Re: DDS4 - hardware compression not working |
|
|
"Steve Cousins" <steve.cousins@maine.edu> wrote in message
news:44F352B1.6090405@maine.edu...
| Quote: |
Larry Hodges wrote:
"Mike Tomlinson" <mike@NOSPAM.jasper.org.uk> wrote in message
JPGs are already compressed. Trying to compress already-compressed data
usually only makes it larger. This could be why the tape is filling up;
the fact that it fills up at or about its uncompressed capacity is a
coincidence.
I thought that might be the case also. So last night I selected various
folders, all containing just data and program files, and the same thing.
Using software compression, I was able to get 26gb on a tape. But with
hardware compression, they recommend you not use software compression.
I've found that hardware compression is not is good as software
compression (my comparisons were with DLT/SDLT vs. gzip). So, in your
test, hardware compression may still be "working" but it may not look like
it is. You should test it with something really compressable like text
files or postscript files. Make a directory of a few large PostScript
files and then keep on copying them recursively into new folders, doubling
your the space used each time you copy. It shouldn't take _too_ long to
get 30 GB say. This should easily fit on a 20GB tape with any sort of
standard compression. It would be a lot easier in Linux using dd or a
short script.
|
The hardware compression on this drive is DDS-DC, using Lempel-Ziv data
compression (also known as DCLZ). I'll try the above test without software
compression and see what I get.
Thanks for the email of this btw. I see you figured out to delete the "2"s.
:)
-Larry |
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Larry Hodges
Guest
|
| Posted: Tue Aug 29, 2006 12:24 am Post subject: Re: DDS4 - hardware compression not working |
|
|
"Jeremy Boden" <jeremy@jboden.demon.co.uk> wrote in message
news:1156800409.14520.10.camel@localhost.localdomain...
| Quote: | On Mon, 2006-08-28 at 10:12 -0700, Larry Hodges wrote:
"Mike Tomlinson" <mike@NOSPAM.jasper.org.uk> wrote in message
news:Sst3PMCs6q8EFwrg@jasper.org.uk...
In article <BOKdnZ1x6MZwNm_ZnZ2dnUVZ_vGdnZ2d@comcast.com>, Larry Hodges
2larry2@2maximizesoftware2.com> writes
I'm prompted for a 2nd tape. I'm using NTBackup, the built-in
backup
app
with x64. I've tried it with and without software compression
enabled.
That suggests to me that the drive cannot further compress the data
it's
being sent.
Maybe half of the data are JPGs.
JPGs are already compressed. Trying to compress already-compressed
data
usually only makes it larger. This could be why the tape is filling
up;
the fact that it fills up at or about its uncompressed capacity is a
coincidence.
I thought that might be the case also. So last night I selected various
folders, all containing just data and program files, and the same thing.
Using software compression, I was able to get 26gb on a tape. But with
hardware compression, they recommend you not use software compression.
...
Obviously the hardware compression can't compress something that's
already been compressed by software (otherwise the software could be
re-written to make a better job of compression...).
Treat jpg and exe files as not worth compressing, database as fairly
compressible (usually). Note that it is usual to quote a 2x factor for
compression - even though you will need some very special data to
achieve this!
|
Well, I got the drive used for $58 (it was actually new...still had the
sticker across the LEDs on the front), so even if I can't get compression
working, I'm still a happy camper  . However, the hardware compression
isn't working at all. At 20gb (+- 200mb), of calculated size, it's asking
for another tape. Even excluding JPGs, AVIs, etc.
| Quote: | Is there any reason why you should not use a second tape?
How about using an incremental backup strategy?
--
Jeremy Boden
|
I would rather put a tape in at the end of the day and start backup. When I
get back into my office, pop it out and put it away and start working. But
if two tapes is the only way to make it work, I'll deal with it.
-Larry |
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Larry Hodges
Guest
|
| Posted: Tue Aug 29, 2006 12:24 am Post subject: Re: DDS4 - hardware compression not working |
|
|
"Mike Tomlinson" <mike@NOSPAM.jasper.org.uk> wrote in message
news:qwn5oSDEV28EFwN6@jasper.org.uk...
| Quote: | In article <Y_CdnUC31p9ivm7ZnZ2dnUVZ_rydnZ2d@comcast.com>, Larry Hodges
2larry2@2maximizesoftware2.com> writes
But with
hardware compression, they recommend you not use software compression.
Agreed.
Obviously, this issue doesn't belong on the SCSI ng.
I don't see that it's a problem posted here.
Problem is, I bought the drive used. In addition, Seagate no longer
supports these drives, but rather Quantum. However, the drive is still
current and can be purchased new. I've emailed Quantum. I'll see what
they
say.
One last thought - have you checked the DIP switches on the drive?
Usually, one of those is to enable/disable hardware compression.
|
Yes, DIP switches are enabled for hardware compression. Under Device
Manager / Tape Drive / Properties, it says enabled = true.
Still haven't heard back from Quantum. If they respond, I'll post here with
their input.
Thanks everybody for your input. I appreciate the help. Any other
thoughts, post them please. I check here daily anyway since I'm a SCSI guy.
Not a lot of us anymore you know...
-Larry |
|
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Larry Hodges
Guest
|
| Posted: Tue Aug 29, 2006 12:24 am Post subject: Re: DDS4 - hardware compression not working |
|
|
"Folkert Rienstra" <see_reply-to@myweb.nl> wrote in message
news:44f36857$0$97225$892e7fe2@authen.yellow.readfreenews.net...
| Quote: | "Larry Hodges" <2larry2@2maximizesoftware2.com> wrote in message
news:BOKdnZ1x6MZwNm_ZnZ2dnUVZ_vGdnZ2d@comcast.com
"Michael Baeuerle" <michael.baeuerle@stz-e.de> wrote in message
news:gnhas3-4vl.ln1@micha.freeshell.org...
Larry Hodges wrote:
I have a DDS-4 Seagate 40 (also called an Archive Python), model
STD62401LW-S. It's 20gb native, 40 gb compressed. However,
apparently
compression isn't working. I conclude that because at 20gb into the
backup,
I'm prompted for a 2nd tape. I'm using NTBackup, the built-in backup
app
with x64. I've tried it with and without software compression
enabled.
What data are you writing on the tape? Some types of data like audio or
video cannot be compressed at all or at very bad ratios by the lossless
compression algorithm used in DDS drives.
Micha
Maybe half of the data are JPGs. The rest, website backups, database
apps,
installation packages, deployment packages, programming projects, Word
and
Excel docs, etc.
I've run a test application that says compression is working properly.
However, I'll go to do a backup. The pre-compressed calculations will
say 26gb.
In my way of thinking,
Which is?
that should fit on a 40gb compressed tape.
And why is that, in the absence of a 'compressed calculation'?
What are the prerequisites for getting 40GB on such tape?
I'll bet it is maximum compressible data and full uninterrupted streaming.
So how do you insure the streaming part?
|
You may have a point Folkert. I've watched the data stream, and it starts
around 320mb/m, but slows through the backup to around 160mb/m. I have a
dual channel card...39320A. (It's in a standard PCI slot, not PCI-X.) Raid
is on B. On A, the tape, a U320 HDD, a U160 HDD and an old Ultra2 Wide HDD.
This may be the entire issue. The SCSI channel is saturated, data stream
slows and hardware compression turns off?
| Quote: | It doesn't. I tried StompSoft's BackupMyPC tonight with the same
results.
That's a nice application btw. The only non-enterprise level backup app
that backs up open files. Only about $40 too. Also works great on x64.
Roxio doesn't.
Any other ideas?
Make an image backup?
|
What's an image backup?
And, thanks for the input Folkert. I appreciate the input.
-Larry |
|
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Timo Felbinger
Guest
|
| Posted: Tue Aug 29, 2006 2:24 pm Post subject: Re: DDS4 - hardware compression not working |
|
|
On Mon, 28 Aug 2006, Larry Hodges wrote:
| Quote: |
Thanks everybody for your input. I appreciate the help. Any other
thoughts, post them please. I check here daily anyway since I'm a SCSI guy.
Not a lot of us anymore you know...
|
Ok, so here's another thought: what tape block size did you choose?
ISTR that hardware compression works per tape block; if you stick with
a small default block size (often 512 bytes for DDS), the drive will
have to compress a huge number of tiny chunks, each one individually,
which will give a lousy compression ratio for most kinds of data.
Cheers,
Timo
--
Timo Felbinger http://www.felbinger.net
Quantum Physics Group Phone: +49 331 977 1793 Fax: -1767
Institut fuer Physik Mobile: +49 177 735 1936
Universitaet Potsdam, Germany PGP key-id: E92567B2 |
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Larry Hodges
Guest
|
| Posted: Wed Aug 30, 2006 4:02 am Post subject: Re: DDS4 - hardware compression not working |
|
|
"Timo Felbinger" <Timo.Felbinger@physik.uni-potsdam.de> wrote in message
news:Pine.LNX.4.58.0608291154480.2834@uranos.quantum.physik.uni-potsdam.de...
| Quote: |
On Mon, 28 Aug 2006, Larry Hodges wrote:
Thanks everybody for your input. I appreciate the help. Any other
thoughts, post them please. I check here daily anyway since I'm a SCSI
guy.
Not a lot of us anymore you know...
Ok, so here's another thought: what tape block size did you choose?
ISTR that hardware compression works per tape block; if you stick with
a small default block size (often 512 bytes for DDS), the drive will
have to compress a huge number of tiny chunks, each one individually,
which will give a lousy compression ratio for most kinds of data.
Cheers,
Timo
--
Timo Felbinger http://www.felbinger.net
Quantum Physics Group Phone: +49 331 977 1793 Fax: -1767
Institut fuer Physik Mobile: +49 177 735 1936
Universitaet Potsdam, Germany PGP key-id: E92567B2
|
Current settings...
Default Block Size: 16384
Maximum Block Size: 8388608
Minimum Block Size: 1 |
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