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Issues with newly purchased LTO-1 tapes

Torolf Haug
Occasional Contributor

Issues with newly purchased LTO-1 tapes

I recently purchased 20 HP genuine LTO-1 tapes, the same model tapes I've been using for years in my 1/8 autoloader with BackupExec. What I've found is when I use tapes that I've previously purchased in 2010 and earlier, the nightly backup job completes in about 3 hours and spans two tapes. This has been very consistent for months.

When using newly purchased LTO-1 (C7971A) tapes, the backup window is now 4+ hours and spans three tapes. Looking at the job logs and comparing them, the hardware compression is much worse, forcing it to write more data and take more time to complete.

This just seems very odd, since it appears to be all of the tapes that I recently purchased that experience this issue. After years of buying tapes, I've never had an issue like this. Anyone else seeing issues with new tapes not performing as well as older ones?
Marino Meloni_1
Honored Contributor

Re: Issues with newly purchased LTO-1 tapes

If you noticed the compression ratio of your backup has changed and this is the cause of the higher anount of data been physically written, then this has nothing to do with the Tape itself.

The Hardware compression is made by the LTO drive at a hardware level, then the compressed data are sent to the tape.

The compression ratio is not under the control of the tape or the drive, the algorithm is still the same and noting in the LTO or Tape can change it.

The compression ration change can only depend of you data.

Other reason may cause your behavior, if the data are not costantly flowing to the LTO drive and the LTO have to wait for data, it may loose some space on the tape, ending up in putting less data.
Another reason may be you have a dirty/worn read/write head, so data are written badly and the read after write process identify an error and rewrite the same data, this also end up in taking more space for writing the same amount of data.

Finally if you think everything is ok, you can use the tests present in LTT to sort out the problem.
You can use the system perf restore test to write an know amount of data to your hdd, let's says 200GB of data with 2:1 compression ration (better use 190GB so you have space for the overhead )
Then you can use this amount of data to write on a 100GB cartridge, and see if you can fill it completely.
In this way you can also check and validate compression is working as expected.
In case of problems, you can collect a support ticket immediately after the test and review it and see the reason for the failure or for not beeing able to store all the data
Torolf Haug
Occasional Contributor

Re: Issues with newly purchased LTO-1 tapes

Thanks for the response. I'll have to run the LTT tools on this drive and see what happens when I do as you suggest.

The only reason that I feel it is the tapes themselves is because when I go back to previously used tapes, everything goes back to spec. My backup windows restore to normal, and it only spans two tapes. When I use the recently purchased tapes, that is the only time this issue occurs.
Richard Bickers
Trusted Contributor

Re: Issues with newly purchased LTO-1 tapes

For a direct comparison, run the LTT drive assessment test with a new tape and then with an old tape. If you can then attach the EventLog.ltt file we can see the difference. You can see the details if you select 'everything' detail level in the results pane.
That's fairly quick - about 15 mins per test - and will tell us quite a bit about your drive and tapes.
It's more interesting when it's gone wrong