Veritas BE 10 - Compression

[Constantin_Voge]

Hi,

i´ve installed BE 10 5520 with SP1 and the latest driversfor IBM 3581-L28.

The hardware compression is enabled, but the data ist not compressed (1:1). What is wrong?

[Constantin_Voge]

I´ve tested the backup with software compression, but onyl with 0,78:1.

Why can´t BE use the hardware compression???

[ray_littlefie1]

From BE Devices tab, Right mouse click the tape drive -> Properties -> Configuration Tab -> Make sure 'enable compression' box is checked.

[Constantin_Voge]

Hi Ray,

thank you for your tip, but that i have checked. :)

[Deepali_Badave]

Hello,


We would suggest you "Erase" the tape before running the "Hardware Enabled" compression and check the result.



Kindly refer to the following technotes for relevant information
-Title: How to figure out if COMPRESSION is working. How much data can be written to a 12/24 GB tape?
http://seer.support.veritas.com/docs/188539.htm
(Note: This technote contains information related to Netware, however we would suggest you to read it) .
For further information, please refer the technote below:
Title: Backups fail to get double the amount of the native capacity recorded to a media, even when hardware compression is being utilized.
http://seer.support.veritas.com/docs/199542.htm


NOTE : If we do not receive your reply within two business days, this post would be marked assumed answeredand would be moved toanswered questions pool.

[Constantin_Voge]

Hi,

the tape was new and no data was written before.

I´ve eraesed the tape and written a new task with a big excel-file (7MB) and "Hardware Enabled" compression. But the data is written 1:1!!!

What the hell is going on?

[Constantin_Voge]

Next step: a brand-new media and the result: the same s....!

[Constantin_Voge]

I´ve installed Windows Server 2003 again with BE 10 5520 SP1 and VERITAS-Drivers für backupdevices.

And the same result: data (excelfile 7MB) is written 1:1!

[ray_littlefie1]

Constantin-

I'd like to make a comment/suggestion: Backing up a 7mb excel file may not be the best sample to test compression with.
Question- If you compress the same file using Windows compression (Right mouse click -> Properties -> Advanced -> Compress) Then compare the file size to file size on disk what is the ratio of the on disk compression of file? (undo the compression when your done).

As a suggestion, what is the size of the \veritas\NT\Backup Exec\Catalogs directory? If you back that up to a scratch tape what is the compression? Because these files will be similar in format to all the readers in this forum you can compare results. Personally, I backup this directory daily and get better than 2:1 compression on these file types.

[Constantin_Voge]

Hi Ray,

thank you for your post(s). :)

The file size of the excel file is, after the windows compression, 2,69 MB.

The size of %program_files%\VERITAS\Backup Exec\NT\Catalogs is 1,25 KB. A little bit small? :)

Should i backup the complete VERITAS directory? -> 425MB

[ray_littlefie1]

You can give it a shot and see how it turns out.

Also, I'm not familiar with your autochanger, but does it have a web interface to modify settings?
Take a look and see if the LTO drives have a setting for compression (on/off/auto). I always set the drive compression 'off' on the hardware and let the software (Veritas) configure the device for compression. I believe either way the data gets compressed, but the software reports incorrectly.

[Constantin_Voge]

Hi,

i´ve backed up the VERITAS directory with 2:1!

But when i backup a directory with different files ( 2,42GB) an no compression in BE, it writtes the files with 0,557:1! The size of the files on the media is bigger (4GB) as on the hard disk. I don´t know whats going on!

Before i written the media, i ereased the tape. Available storage location is 186 GB. After the backup (Files with 2,42Gb) the available storage location is 182 GB! ????

The autoloader have a web interface, but i can´t set the drive compression (that is also the state of IBM-Hotline). It is set always to YES.

I know that my english is not the best! :) But i hope you can understand me!

[ray_littlefie1]

OK- By backing up the Veritas directory with 2:1 compression, it shows that your settings are correct for both the hardware and software.

Regarding the 2.42GB job, can you tell me what backup method you are using. This is in the job Properties -> Settings -> General Backup Method.

Also, can you look at the job log and tell us how many directories and files are being backed up.

I have never experienced compression as low as 0.557:1, but I have experienced compression less than 1:1. It is usually caused by an excessive amount of very small files and empty directories. Directories require space on tape, but do not refelct as data (bytes) being backed up- resulting in a compression ratio of less than 1:1.

[ray_littlefie1]

I'm looking at your post again. You wrote:

But when i backup a directory with different files ( 2,42GB) an no compression in BE , it writtes the files with 0,557:1!

The backup job should have hardware compression enabled in the job properties. Properties -> Settings -> General Compression Type-> Hardware If available otherwise none. Please confirm.

I hope I didn't confuse you with my earlier post regarding compression settings on your IBM tape library.

[Constantin_Voge]

Hi ray,

the backup methode is "entirely - use archives bits".

I´ve wrote the backup again (after deleting the media slowly) - with software compression. The result: 0,375:1!

The job log (xxxx.xml):

7110 files in 917 directorys. Rate: 1348 MB/Min

software-compression-rate: 1,3:1

I´m confused on the software-compression-rate! On the console it is 0,375:1! Also on the console the available space on the media tape is 182 GB of 186 GB. If is correct, then 4 GB is written to the tape. But in the job log the rate is 1,3:1 ???

[Constantin_Voge]

Ray?

[ray_littlefie1]

I don't know.

From what you have posted earlier- the data you are attempting to backup should have compression better than 1:1.

I think it is working, but it is not logging correctly.

Are you using Veritas or IBM drivers for the LTO tape drives?

Recommend using the Veritas drivers.

[Constantin_Voge]

At first i used Veritas- and then IBM-drivers (both new releases). Both with the same result of compression and performance!