Our last two full backups, which run every Friday have suddenly increased in Elapsed Time and reduced Job Rate (our differential look fine), to the point that their running into Tuesday Morning for Verify (usually verify finishes early Monday AM). There have been no changes (even if there was I would expect to see the differential reported differenty) to the server OS that I can see. Also, the byte count compared to one of late July is the same (file count and area size aren't that different) but it now requires two additional tapes (800gb/1.6tb). The only obvious observation is maybe a tape clean will help but any other thoughts on these additional times and tapes required? I can see the Compression Ratio is 1:1 but two additional tapes and no apparent byte increase is not logical

Compression plays a major role in the number of tapes required. 1:1 = no compression at all which will mean additional tapes. Have you made sure there are no maintenance tasks starting on a Friday night? AV scans, Windows, storage/server maintenance, application maintenance etc? Also, check the write statistics on the tapes to rule out Hard Write Errors = problems and the tapes can probably be replaced. You should also download your tape manufacturer's diagnostic utility and, after stopping the BE services, run a write test with compression to see if this is working. Thanks!

I'm just not convinced how the 'near' same byte count can all of a sudden require 2 x additional 800gb native tapes (It's bad enough when you see the 'Data' written is so low compared to the used capacity). It doesn't fill one with confidence seeing 370gb media full on a 800gb / 1.60tb, then you calculate 12 x 800gb native whiich reads even worse. There are no tasks on this server and nothing new has been added anywhere. I'll run some tools and report back, as well cleaning the heads. Thanks

Are you stating that your tapes are getting marked as "full", even when they only have 370 GB, which is well short of the native 800 GB capacity? It sounds like you may have a clogged tape head. This technote should help. http://www.symantec.com/docs/TECH193200

It could also be that the tapes are bad causing a lot of retries and having a lot of areas marked as unusable, thus reducing capacity and increasing backup time. Check the error counts of the tapes, especially the hard errors. You should try using some new tapes.

Yes Larry, that's correct. Thanks, I'll have a read and report back. pkh, these were new tapes that we used

Elapsed Time increase, Job Rate reduction and more tapes required

CraigV
Moderator
10 years ago
Compression plays a major role in the number of tapes required. 1:1 = no compression at all which will mean additional tapes.

Have you made sure there are no maintenance tasks starting on a Friday night? AV scans, Windows, storage/server maintenance, application maintenance etc? Also, check the write statistics on the tapes to rule out Hard Write Errors = problems and the tapes can probably be replaced.

You should also download your tape manufacturer's diagnostic utility and, after stopping the BE services, run a write test with compression to see if this is working.

Thanks!
Marcopolo
Level 6
10 years ago
I'm just not convinced how the 'near' same byte count can all of a sudden require 2 x additional 800gb native tapes (It's bad enough when you see the 'Data' written is so low compared to the used capacity). It doesn't fill one with confidence seeing 370gb media full on a 800gb / 1.60tb, then you calculate 12 x 800gb native whiich reads even worse.

There are no tasks on this server and nothing new has been added anywhere.

I'll run some tools and report back, as well cleaning the heads.

Thanks
Larry_Fine
Level 6
10 years ago
Are you stating that your tapes are getting marked as "full", even when they only have 370 GB, which is well short of the native 800 GB capacity?

It sounds like you may have a clogged tape head. This technote should help.

http://www.symantec.com/docs/TECH193200
pkh
Moderator
10 years ago
It could also be that the tapes are bad causing a lot of retries and having a lot of areas marked as unusable, thus reducing capacity and increasing backup time. Check the error counts of the tapes, especially the hard errors.

You should try using some new tapes.
Marcopolo
Level 6
10 years ago
Yes Larry, that's correct. Thanks, I'll have a read and report back.

pkh, these were new tapes that we used
Marcopolo
Level 6
10 years ago
Quick question about the compression test referenced in the document above. Can I use a new tape for the test, or do I need to use an existing tape?
pkh
Moderator
10 years ago
You still need to check the error count. If they are high for all your new tapes, then there is something wrong with the tape drive
Marcopolo
Level 6
10 years ago
There's 160 soft write errors on one tape and 333 on the other, so I'm not too worried about those.
Marcopolo
Level 6
10 years ago
Just to clarify this, Under Devices and viewing each media slot.

Appendable Until field reports (Media Full)

Used Capacity field reports 779.8GB of 781.5GB which looks correct

Data field fluctuates as mentioned, never reaches anywhere near 780gb
pkh
Moderator
10 years ago
The actual amount of data that you can put on a tape with compression is highly dependent on your data. If you are compressing darts which are already compressed like zipped files, movies and sound clips then you may end up with more data then you started with. See my article below https://www-secure.symantec.com/connect/articles/compression-short-explanation