Cannot Use Full Native Capacity on LTO

[Keith W]

I have a HP Ultrium 960 LTO drive (in a rack enclosure).

It has a native capacity of 400GB (800GB compressed).

Using Backup Exec I have been doing backups without problem for several months.

I backup less that 400GB so have compression turned off for speed.

Recently however, it has started requesting a second tape at 350GB.

I have tried erasing the tapes but still it randomly stops at around 350GB and asks for another tape.

The tape cannot be full as it has another 50GB to go, so what could be causing this?

Could it be drive related? And if so, what coul dbe the cause?

Thanks

[Lewis Finch]

Kieth, There are several things to consider. First, The tape does require some overhead information, file structure, location of data, etc so that is taking some space. Second, hardware compression is turned on by default so you are right not to enable software compression. Third, not all data compresses at 2 to 1. It's just an industry standard we use. And fourth, If the tape drive is shoe-shining (stopping and starting) you will lose some space there as well. Here is a useful document that may help you.
http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=lpg50460

[Keith W]

Thanks for the reply.

What I find odd is that some days it works fine and others it stops.

Our data size generally increases day on day so one day it will stop at for example 353GB of 360GB Total, and the next day will backup a full 362GB for instance.

This makes me believe it's not an overhead issues or anything data related.

As it's different tapes, and even a clean erased tape, it seems not to be the tapes either.

Very annoying though.

Trying a new tape tonight, but no gaurantee it was going to fail if we didn't as it's not every night.

[Richard Bickers]

You should be able to find out what's going on by pulling an LTT support ticket after the backup has finished. Lots of useful information in there (from the drive's perspective).

Take a look at:
* Drive->Health->Device analysis to check for any health warnings
* Drive->Configuration to check that hardware compression is on
* Drive->Performance to see what compression ratio you are getting
* Catridge->Usage to see what native capacity you are getting on to tape
* Cartridge->Health to check that the data is being written to tape OK

As Lewis says, always use HW compression (in the drive on) and SW compression (by the app) off. HW compression can actually speed up your backup (if your system can keep up) and give you more tape capacity.

If you need help with the support ticket you can attach it and we'll take a look.

See http://www.hp.com/support/lttfaq for a quick guide to using LTT.

[Keith W]

A new unused tape failed at 330GB or 360GB total last night.

I have run the LTT support ticket with the following results. Any help with this would be appreciated.

Only warnings under device analysis show hardware compression off. I have turned this on for tonight, but obviously this should not have stopped 330GB being written to a 400GB native tape.

Cartridge Health shows a warning for "Data on Tape" with the result as "Worst <-100%". If you drill down here there are lots of warnings starting "Wrap" followed by a sequential 2-digit number. Each with varying % ratings from 79% up.

Catridge Capacity show the tapes native capacity to be 400GB, the native data written to be 330GB but that the tape has 399GB native capacity used.

This does show then that the tape is full, but how can a 400GB tape be full with only 330GB written to it. Could this be a drive issue, as it is happening with both old, old but erased, and new tapes. One day a failure, the next it works!

Very odd, but quite problematic.

[Richard Bickers]

It's beginning to look like you have a drive problem - which is odd as these drives are pretty good and last a long time in the right environment.

Please run the LTT LTO drive assessment test with a tape you believe to be good. New is best but worst case the test will ask you to run it again with a second tape just to be sure. The test takes around 15 minutes to run.

Have a look through the results. Perhaps post the ResultLog.ltt file (install dir/logs) for us to look at.

Good luck!

[Richard Bickers]

Keith. From what you say I'm wondering if you have a contamination/environment problem. Please take a look at these troubleshooting notes:

http://h41206.www4.hp.com/webapps/IV3/node.iv?locale=en_us&prodSeriesId=238671&node=prodITRC%2FDE_HS_STORAGE_pl3c_EN_01_E%2FN1%7C15%7C29&prodTypeId=12169&serverId=1#src

[Keith W]

Thanks for the reply.

I am running the drive assessment test now so wil post back with the results later.

I think I can rule out environmental. The drive is rack mounted (high up) in a room with minimal dust and no passing people etc. Room is kept locked and only IT staff have access to change tapes work on servers etc.

The room is air conditioned and the vent will blow towards the equipment, but there is no debris etc. so should not be an issue - there is certainly no dust/debris build up on anything.

Tapes are kept in a locked fire-proof safe and only removed to change them. At which point they are handled carefully.

[Keith W]

Test results below:

First tape was a used and successfully completed backup tape from last week. This failed (as yo ucan see below) indicating the drive had a problem.

The second tape was a new, freshly unwrapped tape.


|__ Test 'LTO Drive Assessment test' started on device 'HP Ultrium 3-SCSI' at address '3/0.3.0'
|__ Please confirm that a test cartridge is loaded into the drive (CAUTION: any data on the cartridge will be lost). Continue with the test?
|__ The drive may be suffering from a Write/Read problem. Please insert an alternate test cartridge to verify the drive's performance (CAUTION: any data on the cartridge will be lost). Continue with the test?
|__ The LTO Drive Assessment Test failed. Please refer to the Test Results for further information.
|__ Failed
|__ Analysis Results
| |__ LTO Drive Assessment Test, version V19.08.2005
| |__ Product ID is Ultrium 3-SCSI
| |__ version: V31.11.2005
| |__ Firmware rev G2AD is up-to-date for Ultrium 3-SCSI as of Mon Jun 13 19:00:00 2005.
| |__ Rule 19:
| |__ The drives hardware compression algorithm is currently switched off.
| |__ This was probably set by the backup software.
| |__ The drive's setup has not been altered.
| |__ There were 18 rules checked.
| |__ Device Analysis has checked the historical information and warnings have been reported.
| |__ Testing has completed and some problems were found.
|__ Operations Log
|__ executing LTO Drive Assessment Test...
|__ analyzing device data...
|__ updating device writeback data...
|__
|__ checking for tape loaded...
|__ SCSI parity check...
|__ writing ...
|__ writing block 30000 of 300000...
|__ writing block 60000 of 300000...
|__ writing block 90000 of 300000...
|__ writing block 120000 of 300000...
|__ writing block 150000 of 300000...
|__ writing block 180000 of 300000...
|__ writing block 210000 of 300000...
|__ writing block 240000 of 300000...
|__ writing block 270000 of 300000...
|__ writing block 300000 of 300000...
|__ rewinding ...
|__ checking for tape loaded...
|__ writing ...
|__ writing block 30000 of 300000...
|__ writing block 60000 of 300000...
|__ writing block 90000 of 300000...
|__ writing block 120000 of 300000...
|__ writing block 150000 of 300000...
|__ writing block 180000 of 300000...
|__ writing block 210000 of 300000...
|__ writing block 240000 of 300000...
|__ writing block 270000 of 300000...
|__ writing block 300000 of 300000...
|__ rewinding ...
|__ LTO Drive Assessment Test Finished...
|__ Test failed

[Richard Bickers]

The assessment test the one we ask customers to run for a black/white verdict on their drive. Sometimes it needs to run on a second tape just to differentiate between a drive issue and a tape issue.

Having done this, it would seem you really do have a bad drive. That's not good. Only thing I can suggest is to try a cleaning tape - maybe a couple of times - if you do have some debris in there otherwise you'll have get in touch with HP support, explain what testing you've done and they'll send you a replacement. Are you still under warranty?

[Keith W]

Thank you.

Drive is under warranty.

Will try cleaning tape this afternoon though and report back tomorrow.

[CLin_1]

try to clean 5 times in a row.

[Keith W]

Had the drive replaced under warranty and has not faulted since.

Thanks everyone