DLT 7000 compression problem

[Sachin Soni_1]

Hi ,
I have a dlt7000 ,using it in a compressed mode.
But from last few days i am not able to take backup of more then 35GB.
it says "end of tape detected", and comes out.
I tried creating new device files using "mksf" with -d 133, -I , -C and -c options.

in both "mt" and "lssf" output it shows device configured in compressed mode, while i am not able to use it for more then 35g.
also tried using SAM to create device file , but it gives same error.

anyone know about this problem ??

Thanks,
Sachin Soni

[Vincent Farrugia]

Hello,

This problem emerges simply because the tape can only hold 35Gb of data. It holds 70Gb assuming a 2:1 compression rate.

However, this can be achieved only if the files you care backing up can be compressed. If the files are already compressed, like zip, gz etc, no matter whether you have compression on or not, the DLT7000 tape media cannot hold more than 35Gb simply because it cannot compress it further.

If you are backing up let's say text files, you can most probably store more than 70Gb of such data in a single tape media, because text is easily compressible.

HTH,
Vince

[harry d brown jr]

As Vince has said, a dlt 70 really only holds 35gb of data!

live free or die
harry

[Sachin Soni_1]

Vincent,

i used to take backup of more then 50Gb on same drive.
even today if i access those drives from another box, i am able to take backup of more then 36GB, it works fine.

what i think is :
since its not a software compression , as i am modifying the device files, it should not be affected by the data i am backing up.

Soni

[Helen French]

Hi Sachin =)),

Which device file you are using for taking backup ? If you suspect a problem with the device file, remove it and run 'insf -e'. Or check the major and minor numbers and create a new device file with 'mknod' or 'mksf' command.

Remember, the native capacity of DLT7000 is 35GB.

HTH,
Shiju

[Sachin Soni_1]

shiju darl:)

i did #insf -e

created device files again using SAM

created using #mksf -I -C -c -d 133

didnt help me :(


Soni

[Helen French]

Hey Sachin,

Again, did you check up the setting in the DLT drive (about the compression ratio) ?

Also can you tell me which application you are using for backp (Omniback, Legato, fbackup) ?

Shiju

[Sachin Soni_1]

I guess!!
Bydefault compression is enabled on DLT.

'm using "vxdump"

**
sorry frnds,something personal

shiju baba send me ur phone no's on
sachin369@hotmail

[Aaron Tatone]

Which device are you using? I was always under the impression that to get the HW Compression, you needed to use the BEST device (i.e. /dev/rmt/c7t0d2BEST). Try that and see if that improves anything.

Aaron