DEC abd Tandberg DLT 35/70 Hardware Compression

[fxdwg03]

BE 9.1
Windows Server 2003
DELL Platform
DEC and Tandberg 35/70 DLT external units

Am I to assume that the only way to get hardware compression is to manually press the density override buttons each time?
On the old NT system using pre Veritas BE, once the tape had been written to, it remembered the density override, confirmed by the lights on the unit and did not require intervention.

Thanks

[Aalok_Pathak_2]

There are two types of compression method , Software and Hardware that are available with Backup Exec.


To use Hardware compression, drives should support it.The software compression is performed by Backup Exec application.


When writing to tape media, hardware compression can potentially increase throughput to twice the rate of no compression (provided that the files being backed up are not already compressed or encrypted). While as software compression is performed by the Backup Exec Application; throughput rate is usually the fastest when backing up to hard disk, verses tape media.


Refer Admin Manual for more detais :

http://seer.support.veritas.com/docs/266190.htm

[Vidyaj__Patneka]

Hi,
Kindly update us on the issue.

[fxdwg03]

On a 35/70 DLT unit, do I need to press the denisity override buttons on the front of the tape unit?

Why does BE9.1 not reconize that the tape has previously been written to in hardware compression mode?

[Ken_Putnam]

Why rely on the hardware to detect this? If you want compression (Either hardware or software), select that option in your job.


After having been bitten by differing firmware not reading Hardware compression (both on Compaq DLT7000s), I NEVER use hardware compression anymore. With today's server hardware you will see no difference in throughput and very little if any difference in compression ratios using software compression

[fxdwg03]

I am using hardware compression and I still need to use the density override buttons on the unit.
Do you think that if I do not use hardware compression choice in BE9.1 that it will recognize the compression at the unit??
I know this is a small detail. Everything is working very well but, I just like everything to work as it is supposed to or at least the way I think it should. I just hate pressing the buttons everyday. Now that is lazy I know.

[anoop_nair_2]

Hi,

Unless you press the button to enable compression on the hardware device, there wi;; be no compression. Hence as suggested in the previous post , it is best to enable hardware compression from Backup Exec itself.

[fxdwg03]

Please, Hardware compression is set. It has no effect.
Please advise.

[Ken_Putnam]

From the Devices tab, right click the drive/properties

is "Enable Hardware Compression" selected?

[Vidyaj__Patneka]

Hi,

The hardware compression is vendor specific ( for tape devices). Backup Exec just sends a signal to do a hardware compression, when hardware compression is selected. Thereafter, it is upto the Tape device to do the hardware compression.

The rate of compression depends upon the vendor specification and it differs from vendor to vendor.you can find the information in their respective manuals.

When data is backed up with compression,the compression level varies for different files.For E.g. the executable files,database files are compressed to a less extent as compared to normal data /text files.So the overall compression for the whole data depends upon what kind of data is being backed up.

You may refer the following document,
http://seer.support.veritas.com/docs/199542.htm


Hope this clarifies.

[Sheetal_Risbood]

Hello,

In reference to our previous reply to your post, we would request you to update us on the progress.

However, if we do not receive your intimation within two business days, this post would be 'assumed answered' and archived.


Thanks.

[Sheetal_Risbood]

Archiving the post as per our previous reply