Backup Randomly Exceeds Tape Size?

Question

Hi,&nbsp;

Windows 2008 R2 Server, Backup Exec 2014, LTO-3 Tapes / Drive

I am exeperiencing a strange issue, we backup up pretty much identical data on a daily basis, lets's say for arguments sake, 5GB is the absolute most the backup size will fluctuate.&nbsp;

One day the backup will successfully complete and write the data to tape with a total size of 542GB. The next day I will come in and the backup is stopped waiting for a second tape yet is has only written 535GB?&nbsp;

All tapes are the same HP LTO-3's, backup is set to always overwrite and I have even tried new tapes and run in to the same issue?

Any ideas? I am at a loss :/

&nbsp;

Thanks!&nbsp;

&nbsp;

pkh · Accepted Answer

It depends on the type of data. If somebody happens to save a zipped file or a picture, you can get more data after compression than what you have started with. See my article below.

https://www-secure.symantec.com/connect/articles/compression-short-explanation

It would be easier to just cater for two tapes or get a higher capacity tape drive and tapes

craigv · Answer

...you need to check those tapes to see if compression works on them or not. For this you'd need the tape manufacturer's diagnostic utility and a tape you can overwrite. This will do a compression test on the tape to see what you're getting. It might be a case of LTO3 tapes being old now and not having the same functionality as new.

pkh's suggestion is a good one...LTO5 should be well priced now, depending on your country.

Thanks!

pkh's suggestion is a good one...LTO5 should be well priced now, depending on your country.

Thanks!

ianw82 · Answer

Thanks for the replies, we are in the process of spec'ing the upgrade to LTO-5 but for the time being I would like to get it working.&nbsp;

I did try to download the HP Diagnostic utility but the HP website is succeeding in getting worse everytime I try to use it, I can find the info page about the software but it seems impossible to download, just sends you around in circles&nbsp;- rant over!&nbsp;

&nbsp;

craigv · Answer

Try this link Ian (don't forget that HP have split so this makes things very confusing!):

http://h20566.www2.hpe.com/hpsc/swd/public/detail?sp4ts.oid=406731&amp;swItemId=co_149019_1&amp;swEnvOid=4024

Thanks!

larry_fine · Answer

two guesses:

1) your daily data is just barely going over or under a 1 tape thresh-hold as Cragi &amp; pkh have mentioned.&nbsp; You might investigate software compression instead of hardware compression as apossible workaround, YMMV.

2) you might have old enough tape cartridges or tape drive heads that some of your cartridges actually have a tiny bit&nbsp; more usable space on them.&nbsp; Keep an eye on your soft/hard errors counts for both the media and the drive.&nbsp; Running some extra cleaning cycles or running vendor diagnostics on the tape drive may help also.

&nbsp;

Jumping to LTO5 might be a wise move as that still allows you to read &amp; restore your existing LTO3 cartridges.&nbsp; If you jump to LTO6, then you cannot read your old tapes.&nbsp; You will possibly also be switching from parallel SCSI to SAS when you upgrade tape drives.&nbsp; Just make sure that you use a SAS HBA that supports tape.&nbsp; Generally that means simple (non RAID) cards, unless it is listed as supported at http://www.symantec.com/docs/TECH70907

pkh · Answer

SW &amp;  HW compression gives roughly the same result so there is not much point in investigating SW compression if HW compression is working

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Backup Randomly Exceeds Tape Size?

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