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DAT - Hardware compression DAT

Andersen
Advisor

DAT - Hardware compression DAT

Hello. I am using DAT72 and TapeWare as backup system. Recently I have become rather close to some 36GB to backup, and TapeWare starts returning Warning 1301 and Error 1303 because of the drive having problems writing.

It says: "Your tape drive is having problems writing data. No data has been lost but there has been a reduction in the capacity of the tape."

When I reduce the size of the set, the error does not appear. I dont use compressed partitions, hardware compression is ON at the drive and in TW advanced option and the Compression type is "System" so I would expect some significant headroom on top of the 36GB (uncompressed capacity) of the drive.

This appears not to be tha case. Can anyone please give me a hint on what is wrong?

Thanks for reading and replying.
12 REPLIES
Torsten.
Acclaimed Contributor

Re: DAT - Hardware compression DAT

Best idea would be to use LTT, do an assessment test and pull a support ticket for review.

http://www.hp.com/support/tapetools

Hope this helps!
Regards
Torsten.

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Andersen
Advisor

Re: DAT - Hardware compression DAT

Thanks for the proposal. Attached LTT html-report taken immediately after Drive Assessment Test.
Andersen
Advisor

Re: DAT - Hardware compression DAT

... followed by a LTT html-report taken immediately after Data Compression Test.

During this test a compression factor of above 2 is found where the compression factor in the Drive Assessment Test report above is below one.

If these figures are correct I may be better served turning hardware compression off in daily use!

From my experiences with software compression tools much of the data - roughly 50% - can be compressed by a factor 4:1. So I expect the DAT72 drive to be able to store more than what I see here.

Thanks again, and hope someone can guide me to a solution.
Torsten.
Acclaimed Contributor

Re: DAT - Hardware compression DAT

Can you please attach the original lzh file?

Hope this helps!
Regards
Torsten.

__________________________________________________
There are only 10 types of people in the world -
those who understand binary, and those who don't.

__________________________________________________
No support by private messages. Please ask the forum!

If you feel this was helpful please click the KUDOS! thumb below!   
Andersen
Advisor

Re: DAT - Hardware compression DAT

A LTT data .lzt file created immediately after a Drive Assessment Test is attached. Thanks for your support.
Víctor Cespón
Honored Contributor

Re: DAT - Hardware compression DAT

Mixed results...

Device Analysis : Failed
Serial EEPROM Data is not accessible on this drive
Write (last 8 tapes) : Good Margin (62.2 GB)
Read (last 7 tapes) : Good Margin (39 GB)
Load/unload life : Great margin, 97% life remaining
Write Compression Ratio : 1.2:1 (last 32.5 GB)
Read Compression Ratio : 1.2:1 (last 29.2 GB)
Power on time : 180 days, 9 hours, 0 minutes
Load/Unload cycles : 234 (2% of expected life)
Trygve Henriksen
Respected Contributor

Re: DAT - Hardware compression DAT

How old are the tapes?

DAT tapes are VERY fragile and(in my experience) prone to stretching. Also, tapes used in one drive was often found to be unreadable in another.
(Its over a decade since we scrapped our last DAT drive and went for DLT, then SDLT, and these days LTO4.)
Andersen
Advisor

Re: DAT - Hardware compression DAT

I would say that some of the tapes may have been written to some 50 times and we use full validation so those of the tapes may have been "rolled out" 100 times. If it is tape wear - is there a recommended lifetime?
Trygve Henriksen
Respected Contributor

Re: DAT - Hardware compression DAT

Well, my preferred 'lifetime' for DAT is the amount of time it takes me to bin them, but that's my opinion.

50 times may be 'cutting it close' so to speak.
We used sets of 20 tapes back then, with a 4 week rotation, and occasionally swapping out a tape to store off-site as monthly, quarterly or yearly backup, and tapes that wasn't rotated generally got junked after 2 - 3 years at the max.
(Each tape was used 12 or 13 times/year, so... )

The problem is that the tape is so thin and narrow that it takes almost nothing to stretch it.
The 'almost nothing' in this case being the speed modern DAT drives use, combined with rapid spooling back and forth, particularly when doing a restore...

I think there was once systems that used VHS tapes, which were less reliable than DAT...
(8mm video tapes just about tied with DAT)
Andersen
Advisor

Re: DAT - Hardware compression DAT

Thanks for sharing your experiences. I will consider replacing the set of tapes with fresh ones. What puzzles me is that the error seems to pop up near the end of the tape. I would expect tape wear and stretch to be most prominent in most frequently used part of the tape - i.e. the beginning rather than the end.

I also looked for hardware upgrading to the DAT160 but I am not sure if they can be used with the NT4.0SP6 Server.

http://h10010.www1.hp.com/wwpc/us/en/sm/WF06b/12169-304612-3446234-3446234-3446234-63890-3542583-3542584.html
Andersen
Advisor

Re: DAT - Hardware compression DAT

So I decided to replace all cartridges in my working set. As can seen from the TapeWare log below the behavior remains.
Attached is also a recent LTT support ticket which seems to confirm the amount of written data (22.7GB)

Any suggestions to what I can do with a drive that seems to be full when only 22GB is written?

Thanks again for reading and replying.


===============================================================================
Job Backup af E: og G:
===============================================================================

Summary
-------------------------------------------------------------------------------
Job Type : Backup Job
Number of Passes : 3
Logging Mode : Failed Objects Only
Backup mode : Full
Change mode : Skip device
Write Mode : Overwrite all Media
Auto Format Mode : Auto Format Blank Media
Verify Mode : Full Data Verification

Job Start Time : 14-Jun-2010 07:00 PM
Selecting Objects : Start 14-Jun-2010 07:00:03 PM
Selecting Objects : End 14-Jun-2010 07:04:42 PM
Backup First Objects : Start 14-Jun-2010 07:04:42 PM
Backup First Objects : End 14-Jun-2010 07:04:43 PM
Backup Begin Objects : Start 14-Jun-2010 07:04:43 PM
Backup Begin Objects : End 14-Jun-2010 07:04:43 PM
Backup Pass 1 : Start 14-Jun-2010 07:04:43 PM
:
: Disaster Recovery information has been saved for
: Host : SERVER
: Device : Dev-1.0.3.0: HP C7438A
: Media : Mandag_L
:
:
: ALERT: Warning 1301 : TapeAlert - Warning - Write
:
: Backup af E: og G:
: Dev-1.0.3.0: HP C7438A
: Mandag_L
:
: 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.
:
:
: ALERT: Error 1303 : TapeAlert - Critical - Media
:
: Backup af E: og G:
: Dev-1.0.3.0: HP C7438A
: Mandag_L
:
: Your data is at risk: 1. Copy any data you require from
: this tape. 2. Do not use this tape again. 3. Restart
: the operation with a different tape.
:
Job End Time : 14-Jun-2010 11:36 PM

Effective Throughput : 1424 Kbytes/Second
: 83 Mbytes/Minute

Selected Objects : 158509
Selected Size : 34566834 Kbytes
Completed Objects : 133518
Completed Size : 23625062 Kbytes
Failed Objects : 0
Failed Size : 0 Kbytes

Job Terminated with Error:
76 : Operator cancel

Details
-------------------------------------------------------------------------------
Streams : SERVER\System State
: Selected Objects : 3
: Selected Size : 9996 Kbytes
: Completed Objects : 0
: Completed Size : 0 Kbytes
: Object Warnings : 0
: Object Warnings : 0 Kbytes
: SERVER\E:
: Selected Objects : 70639
: Selected Size : 20284566 Kbytes
: Completed Objects : 56851
: Completed Size : 10832391 Kbytes
: Object Warnings : 0
: Object Warnings : 0 Kbytes
: SERVER\G:
: Selected Objects : 87866
: Selected Size : 14272271 Kbytes
: Completed Objects : 76667
: Completed Size : 12792670 Kbytes
: Object Warnings : 0
: Object Warnings : 0 Kbytes
: SERVER\TapeWare Storage Server Database
: Selected Objects : 1
: Selected Size : 0 Kbytes
: Completed Objects : 0
: Completed Size : 0 Kbytes
: Object Warnings : 0
: Object Warnings : 0 Kbytes
Media : Home\Admin Folder\Mandag_L
: Completed Objects : 133518
: Completed Size : 23625062 Kbytes
Devices : Dev-1.0.3.0: HP C7438A
Andersen
Advisor

Re: DAT - Hardware compression DAT

Follow up: Based on your comments on the support ticket I contacted HP support. The drive was replaced without discussion within 2 days. The backup now seems to complete as I would expect so it was an issue within the drive. Thank you very much for answering to my thread and helping me out and to HP for providing good service.