Compression Ratio Improvement

[RicoLui]

Hi All

Our customer already enable the hardware compression for the backup job & tape drive (HP LTO3) but find that the ratio is not good. They need to use two tape for the full backup. The compression ratio of 1st tape (Slot5 of image1) is only 1.1 and the compression ratio of 2nd tape (Slot5 of image1) is 1.7

Is there any suggestion can improve the compression ratio to complete the full backup job with one tape? Thanks!

image1

One Tape            Backup Thu Full

Byte count          : 459,073,040,204 bytes
Job rate            : 1,196.99 MB/Min (Byte count of all backup sets divided by Elapsed time for all backup sets)

Files               : 464,449
Directories         : 51,628
Skipped files       : 0
Corrupt files       : 0
Files in use        : 0

Original start time : Thursday, December 15, 2011 9:00:00 PM
Job started         : Thursday, December 22, 2011 9:00:00 PM
Job ended           : Friday, December 23, 2011 3:07:14 AM
Elapsed time        : 06:07:14




Two Tape             Backup Fri Full

Byte count          : 460,659,750,180 bytes
Job rate            : 1,209.57 MB/Min (Byte count of all backup sets divided by Elapsed time for all backup sets)

Files               : 465,189
Directories         : 51,708
Skipped files       : 0
Corrupt files       : 0
Files in use        : 0

Original start time : Friday, December 16, 2011 9:00:00 PM
Job started         : Friday, December 23, 2011 9:00:04 PM
Job ended           : Saturday, December 24, 2011 3:07:09 AM
Elapsed time        : 06:07:05
 

[teiva-boy]

The main thing is that the data is not already compressed on the source, or that it's not being done in software first.

Other than that, there is nothing you can do short of having up to date drivers and firmware for your tape devices.  Compression either works or doesn't.  Most manufacturers claim 2:1, often getting only 1:1-1.5:1 at best for an overall average.

This is normal.  You need to fit on X amount of data on Y amount of tapes, move to a larger capacity format like LTO4 or LTO5.

[RicoLui]

Hareware upgrade is the only solution for this case?

[pkh]

Hardware upgrade is only good if there is a problem in the tape drive's firmware which affects hardware compression.  It would be of no use if your data is not amendable to compression, e.g. you are compressing data which are already compressed, like zipped files, movie, sound and picture files.  See my article on this subject

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

Since you are getting 1.7 on your second tape, it means that hardware compression is working.

[Ken_Putnam]

As the others have said, you cannot tweak compression to attain a better ratio.  Compresion is either ON or OFF.  While not identical, HW and SW will  be quite close

If you cannot fit all your data on one tape any more, you have two choices

1)  Split your data into multiple jobs

2)  upgrade your tape Drives to larger capacity models (and buy a whole new set of tapes for all your daily/weekly/monthly jobs )

[RicoLui]

Hi Ken

How about if I split my backup job to two jobs

One for Media/Pics

One for Documents

Is it possible to improve the overall compression ratio and use one tape only? Thanks!

[teiva-boy]

If the goal is to use one tape only, you need to move to a larger capacity tape.  

Splitting jobs will do nothing for you, the tape drive will compress whatever it sent to it, regardless of the number of jobs sent to it.

[RicoLui]

But 400G/800G is the largest capacity for LTO3.

[CraigV]

Hi Rico,

I'll answer both your questions:

1. Splitting your backup jobs means you're still using 2 tapes, but with 2 separate jobs and 2 separate selection lists too. If those photos don't change then you might be better off looking at changing your backup process to DIFF/INCR instead of a full every day. Run the FULL backup over the weekend, and the DIFF/INCR job during the week. You'll be cutting down on the number of tapes used MOnday --> Friday.

2. teiva-boy is suggesting buying a new LTO4 tape drive at a minimum...this would take care of spanning 2 tapes, and you'd still get some (unknown ratio) compression as well whicd would tide you over for a while.

Thanks!

[pkh]

What the other users are suggesting is that you buy a LTO4 or LTO5 tape drive and the corresponding tapes which has higher capacity per tape.