Compression not working PV-132T Library - BE2012

[Christopher_Jol]

Good Morning,

Making major progress with our upgrade to 2012.  All full backups ran this weekend with no errors!! WOOT WOOT!!!

However, I am noticing that none of my jobs are getting any kind of compression when backing up to our Dell PV-132T library.

All jobs are configured to Use Hardware Compress and fall back to software if Hardware is unavailable.  Yet, all tapes used this weekend are showing 1:1 compression.

Also, on a similar line, I have also noticed that if I turn on Encryption, my jobs will not use compression either.

Thoughts?

[Sush---]

Symantec recommends that you avoid using hardware compression with software encryption. Hardware compression is performed after encryption. Data becomes randomized during the encryption process. Compression does not work effectively on data that is randomized.

The above abstract it taken from the technote " http://www.symantec.com/docs/HOWTO73389 "

Thanks,

-Sush...

[CraigV]

Hi,

I don't think that you can use compression when encryption is used. Could be wrong, but I remember reading something around this.

As for not getting any compression, make sure you're using the SYmantec drivers for the tape drive, and if you log onto the web front-end of the library, you can check if compression is enabled there.

Some data won't compress, as it is already compressed...bear this in mind too.

Lastly, make sure that the tapes in use don't have any hard-write errors. If they do, try the backup with a new tape and see if this changes anything.

Thanks!

[Christopher_Jol]

I tried referening to the link you provided but I am wondering if you linked the wrong one?

[Christopher_Jol]

I have modified the compression settings to use Software only and for now have turned off Encryption to see how that affects the jobs.  One step at a time I guess.

[CraigV]

...software compression will use your server's resources so be careful of that. Hardware compression is always better if you can do it.

[Christopher_Jol]

Understood on the software compression.  I do not believe my library can use hardware compression.

Hmm, I take that back,  I just looked at the config settings for each tape device and they both have Hardware compression enabled.  Now I'm confused.  Gonna leave it on software for tonight and see how it runs and will then try hardware tomorrow and compare run times.

[pkh]

If your tape drive support hardware encryption, then you should use BOTH HARDWARE encryption and compression.  Otherwise, use BOTH SOFTWARE encryption and compression.

As previously advised, do not use software encryption with hardware compression.  Your data will not compress and you might end up with more data than you started.  See my article on this subject.

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

[Christopher_Jol]

Thanx for sharing the article, most helpful.  Just for the record, everything ran last night with hardware compression (not the previously stated software) and no encryption.  From looking at the tape, I dont think anything was actually compressed, shows a 1.05 entry under compressed.  Using BE2010 R3 I would normally get close to 2:1.  So, with that said, I have adjusted all the jobs back to just Software compression and no encryption and will see how the jobs run tonight.

I gotta add, for being such a streamlined interface, I am clicking more now than I have ever had to click in this program.

[Christopher_Jol]

Well, the backups ran fine again last night.  Using software only compression it shows 1.03 compression.  So, I am seeing little to no difference between using Hardware and Software compression (no encryption).  I have verified that the library is using Symantec drivers and they are current.

For whatever reason, since upgrading to 2012, we are getting no compression on our jobs.

I am now updating the firmware from Dell for RMU, Library and both drives.

[Christopher_Jol]

So much for updating the firmware, it was already at the latest release.  Now, I am officially stumped.

Compression is not working on LT03 tapes using our PV123T library.

[jpk]

Although i'm not entirely sure what fixed my issue, here is what i did...

After upgrading to BE2012 from BE2010R2, i noticed the same thing; no compression (it took 5 tapes when it normally only needs a little bit more on a 3rd tape).  What i ended up doing what going back into all my jobs and changing it to "hardware compression, otherwise none".  After i saved all my jobs back out i was seeing the compression ratios i had prior (1.7:1 or so).

We are using LTO4 tapes with a Dell TL2000 tape library.

[Colin_Weaver · Accepted solution]

As an update Symantec have found two conditions relating to compression in BE 2012

1) is Do not use the compression setting "Hardware if Available otherwise Software" which is already mentioned in this thread. We are working on a fix for this but for now use "Hardware if available otherwise none"

2) is the Admin console displays the compression as 1:1 - this appears to be a cosmetic/display issue a full backup of a known set of datat to tape as an overwrite and then compare byte count of data set with amount used on tape youw ill find compression has taken place. Agsin we are working on a solution to this.

Of course there may still be an unidentified cause out there so please log cases if the above information does not solve your issue

EDIT:

Anyone who continues to think compression is not working should also review

http://www.symantec.com/docs/TECH50960

And if both the mode_select6 and mode_sense6 commands do show the 7th byte setting compression then you are either backing up data that can't be compressed, or your hardware vendor may need to look at the problem