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DLT 7000 compression problem

Sachin Soni_1
Frequent Advisor

DLT 7000 compression problem


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
N-joy
8 REPLIES
Vincent Farrugia
Honored Contributor

Re: DLT 7000 compression problem

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
Tape Drives RULE!!!
harry d brown jr
Honored Contributor

Re: DLT 7000 compression problem

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

live free or die
harry
Live Free or Die
Sachin Soni_1
Frequent Advisor

Re: DLT 7000 compression problem

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
N-joy
Helen French
Honored Contributor

Re: DLT 7000 compression problem

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
Life is a promise, fulfill it!
Sachin Soni_1
Frequent Advisor

Re: DLT 7000 compression problem

shiju darl:)

i did #insf -e

created device files again using SAM

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

didnt help me :(


Soni
N-joy
Helen French
Honored Contributor

Re: DLT 7000 compression problem

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
Life is a promise, fulfill it!
Sachin Soni_1
Frequent Advisor

Re: DLT 7000 compression problem


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
N-joy
Aaron Tatone
Frequent Advisor

Re: DLT 7000 compression problem

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