Ultrium-3 tape drive compression not working, backing 495Gb data.

[chuong_n]

Hi
Running Brightstor r11.1 on Windows 2003 SP2
with an external ultrium-3 tape drive.
Recently backups has been asking for a 2nd tapes for the full backups. Compression is set by hardware. Used the LLT tool to check data compression and reports show compression is working.
Tape drive firmware: G66D
Media compression ratio 1.43
Backup size 495Gb

Can anyone help?
I've attached the health check report.

[Torsten.]

The LTO-3 has 400GB **native** capacity.



If you read something like

"...LTO-3 delivers 800GB* of compressed capacity..."


watch the "*":

* Assumes 2:1 compression

(taken from quatum website).




This is pure marketing and has **nothing** to do with real life.

[Torsten.]

... and by the way, it looks like your tape is connected to the HBA Model: Smart Array 6i - this is AFAIK not supported!!!

You need a "pure" SCSI controller.

(this will not change the compression, but the reliability).

[Torsten.]

My final comment if you are not so familiar with such kind of compression:
Try to zip a jpeg image for example. The (compressed) result is likely bigger then the uncompressed original file.
Now compress a large text file. The result is likely very, very small.
So you can see, compression does not always produce similar results.

Sometimes you cannot compress some data at all, because it already is.

[chuong_n]

so with my current setup which is backup 495Gb of data will now use 2 tape because compression can't do 2.1 ratio?

What if I disable hardware compression and used software compression?
How can I disable hardware compression?

[Shiju Samuel Thomas]

What if I disable hardware compression and used software compression?
How can I disable hardware compression?

AS no further compression of the data is possible as pointed out rightly by Torsten, you will require a second Tape to backup any data more than the current size.

Hardware compression is on by default. Hardware compression is turned off when you enable Software compression in your backup application.

[S. Boetticher]

you could verify the "compressibility" of your data, if for instance you'd compress it using winrar (or similar) to an external USB harddisk or copy it to external HDD formatted with NTFS (if you use windows) and enable compression.
Both methods should give you an impression how good or bad YOUR data can be compressed.
The 2:1 is pure marketing (becoming worse with LTO-6 and it's 2,5:1).
We've seen anything from 1:1 (jpegs, mpegs) over 1,4:1 (typical windows file servers) to up to 5:1 (database dumps)...