How to disable hardware compression of Surestore DAT24x6 External

[Paul Yeung_2]

I am using Arcserve 2000 with Surestore DAT24x6 External. It seems that the hardware compression is useless and also stops me from using the software compression. However, the hardware compression is set ON by default and it is not possible to set it OFF in Arcserve (unlike single slot models, there is no compression tab in the device manager). Therefore, I would be grateful if anyone can suggest how to disable the hardware compression by default.

[Eugeny Brychkov]

See this http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x72f0cdec06f1d61190050090279cd0f9,00.html (switches setup is the same for all DDS models). Try looking at the unit from the bottom. If you'll find hole with switches - you're lucky, but if not.... then you'll need to open autoloader's case
Eugeny

[Paul Yeung_2]

Thanks Eugeny, I have seen that post before, however there seems no official information from HP regarding the setting of DIP switches. Grateful if you would let me know where can I find an official document showing the setting of the DIP switches.

[Eugeny Brychkov · Accepted solution]

Paul, I did not find official information on the hp.com and I think you'll not find it because HP ships drives with hardware compression enabled and names products accordingly - dat24 (compression 2:1=24GB, compression 1:1=no compression=12GB), dat40 (compression 2:1=40GB, compression 1:1=no compression=20GB)
Eugeny

[nupdyxa]

I found some information here:
http://h20000.www2.hp.com/bc/docs/support/SupportManual/lpv37995/lpv37995.pdf
From my experience under Win2K if all 8 DIPs are ON the DLL Tape Tool indicates that the Hardware compression is OFF. As opposed to that, when the DIP 3 is OFF, the rest are ON, the hardware compression is indicated ON.

[Paul Yeung_2]

Thank you very much for all the replies. I have did a minor research on data compression with Arcserve, and would like to share my findings here.

1. The hardware compression issue is mainly the problem of Arcserve. Arcserve only provides limited support in this area. The hardware compression option is only available for single tape drive. (Not available for x6 / autoloader models)

2. Even there is a compression option to choose from, it is full of bugs. First, Arcserve does not allow change of compression mode if the tape is not BLANK, however, you just like to swap your original tape with a BLANK one, change the mode, and then swap back to your original tape, then you have change the mode you want. So basically this restriction is useless, and ridiculous.

3. No matter if you enable/ disable the hardware compression, when you start/ restart the tape engine, Arcserve will set the hardware compression to ON, regardless the default compression setting set by the DIP switches on the tape drive, unless you have DISABLED host control. Therefore, you can never maintain a job using software compression only unless you never reboots the server or disable host control.

4. The last part is about HP. The tape drive did not report the compression ratio and amount of remaining tape to Arcserve. Therefore you can never know whether a the tape drive has done a good job and whether there is enough space for small backups to append to existing tape.

Just hope that both Computer Associate and HP can do something to improve their programs and drives.