Not getting full back up on 40 GB tape

[sneekn]

We are compressing data on a 40/80GB(DTL)tape, but only getting 28GB before it asks for a new tape...

Any ideas would be greatly appreciated!!

 

[TheLad]

Is that 28Gb uncompressed data or 28Gb compressed data? Also, what OS and version of Arcserve (including patch levels) are you using? What sort of files are you backing up? -----------------------------------------------------
"It's true, its damn true!"
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[hhennessy]

On DLT's the Tape Drive unit is responsible for the compression. As you are using a DLT 4000, you can use 20/40 GB tapes. If compression is turned off you will get 20Gb on to a tape. However, when compression is turned on you can get a theoretical maximum of 40GB (ie a 2:1 Compression Rate), but this depends on the nature of the data you are backing up and hence the compression ratio may not be as good as 2:1. This is probably what is happening in your case. You could consider upgrading your DLT drive unit to a DLT 8000 or an Ultrium Tape Drive Unit(Model : 230E)which takes 100GB/200GB tapes.

Hope this helps.

Cheers,
Hugh.

 

[lucasi]

I'm having this same problem I have a 40/80 tape that is only holding 31.3GB and asks for a new tape. I have to use a second tape for 2.3GB. I understand that if the data is compressed on disk it will not compress further on tape and depending on the compression and the file types I may not get 80GB but I'm not even getting 40GB out of this tape. Any ideas?????

 

[Cyklops]

It is true that you cannot keep compressing data endlessly, but the unit will try to compress the data as far as it's capable of doing so. Did you check if compression is enabled in the ARCserve device manager ?? 32GB isn't very much on a DLT-IV tape.

regards

 

[lucasi]

Yes, compression is set some of the data, we are using 3 tapes for this backup and the first tape holds 46GB and ths second tape only holds 31GB. I don't understand why if we are using the same size tapes aren't we even getting 40GB out of it.