How to do compression on Backup Exec 12?

[Achilles1]

I have server Backup Exec 12 with robotic libriries MSL 6000 Series. One tape have 400 Gigybyte.
In menu options I find "Enable compression".
Here are current settings in Menu
Preffered configuration
Block size (per device) - 64 KB
Bufer size (per device) - 64 KB
Buffer count
Hight water count - 0
Read single block
Write single block - v
Read SCSi pass-through mode
Write SCSi pass-through mode - v

Questions:

1) This option is responsible for compression, if not where I can find it?

2) If this option is true (resposible for esafe), how I can do compression in two, three, four? Have compression influence on speed record on tape?

3) Have new options of compression influence on old backps? They also will be compressed or not, or they will be until delete and new after will be compressed?

4) May be something else?

Thanks all. Sorry for good english.

[pkh]

> In menu options I find "Enable compression".

When you check the "Enable compression" checkbox, it enables hardware compression on your tape drive.

To use compression in your job, in the General settings of your job properties, you can use the Compression type dropdown box to specifty the compression that you want.  This setting will only apply to future backup jobs.  Whatever data that have been backed up previously will not be affected.

[Achilles1]

Thaks! Good answer. But I couldn't not find this options "Compression" in General settings of my jobs properties.
Can you say in detail where I can find it? I listed all options in my shedule jobs and coudn't find it.
???

[pkh]

For compression, see below

[Achilles1]

OK! Thanks! But where I can determine the type of compression? In four, in two, three power? My tape have 400 Gig. Can I determine that it will show 800 Gig with compression. (???)
My  tape can maintain this in properties by default. Where and how I can point this?
nd what influence it will be on speed of backups?

And if it's no so hard can yoг say some words about this properties.... Want to understand what I do...

Block size (per device) - 64 KB
Bufer size (per device) - 64 KB
Buffer count
Hight water count - 0
Read single block
Write single block - v
Read SCSi pass-through mode
Write SCSi pass-through mode - v

???

[pkh · Accepted solution]

You just specify whether you want compression or not.  You cannot specify how much you want to compress the data.  Your tape can handle 400GB without compression and 800GB with compression.  However, the ACTUAL compression ration (compressed vs. uncompressed) will be lower than 2, somewhere between 1 and 2.  How much lower will depend on the type of data that you have.  Some data compress better than others.  The compression ratio depends on the type of data and not on the tape itself.

When you use compression, the backup will definitely be slower.  This is the trade-off for putting more data onto the tape.  How much will compression slow down the backup will depend on a lot of factors, like your hardware, etc.  To know how much compression slows things down, backup the same data twice, one with compression and one without and compare the timing.

[Achilles1]

OK! My last question.
ALL this options was choosen on my shedule jobs (on the picture you download - hardware compression) and this,

Preffered configuration
Block size (per device) - 64 KB
Bufer size (per device) - 64 KB
Buffer count
Hight water count - 0
Read single block
Write single block - v
Read SCSi pass-through mode
Write SCSi pass-through mode - v

The job's worked more then two mounth every day,

but on all tape show 400 Gigs, why not 800Gig? What I didn't do? It must be more 400 Gigs, isn't?

[pkh]

400 GB is the actual capacity of the tape.  When you compress data, you would actually write, say 2 bytes of data for every 5 bytes of "real" data.  That is why 800GB is not shown.  800GB is the maximum amount of compressed data that the tape can handle.

[Achilles1]

In option Devices, when I choose all devices exist option "compression ratio" I can see
5:1 
5, 3:1
4, 3:1
4, 8:1
This is power compression, yes? But if the maximum in two time from 400 to 800? Why 3:1? And what mean for example 4, 8:1 ???
For example 2,4;1 full media have 860 Gigs...

I was inattentive and didn't see that the size of some my backups more 400 Gig inspite of some free size it have on tape)).

[pkh]

Can you post a screenshot of the "compression ratio" that you are talking about?

[Achilles1]

[Larry_Fine]

The compression is a ratio, so it always ends with ":1", so you can basically ignore that.

The first number (the number before the : colon) is the key number.  If is is "1" (i.e. "1:1") then you are effectively getting no compression.  If is is "1.5" (i.e. "1.5:1") then you are getting medium (50%) compression.  If it is "2" (i.e "2:1") then you are getting good compression (100%) and this matches the advertising of most tape drives and media.  I see in your screenshot that you have some high numbers (such as 2.9:1 and 4.8:1), this is highly compressible data and you will get more data per tape than is advertised.