Re: VXA2 tape drive only stores 56GB

Folkert Rienstra wrote:
"Arno Wagner" <me@xxxxxxxxxxx> wrote in message news:4ios53F4q080U1@xxxxxxxxxxxxxx
Previously Andreas Koepke <news@xxxxxxxxxxxxx> wrote:
We recently upgraded from a DDS4 tape drive to an IBM VXA2 and
are having problems with the VXA2 only storing 56GB per tape.

We are using X23 tapes which are meant to store 80/160GB.

Under perfect conditions, no doubt, like maximum compressable data
and perfect streaming, without the drive inserting empty spaces.

"* Tape drives that use data compression technology have storage capacity that will vary depending upon whether the drive is operating in native mode (without compression) or compressed mode. Although the compression technology used in IBM tape drives can typically double the amount of data stored on the media, the actual degree of compression achieved is highly sensitive to the characteristics of the data being compressed."
http://www-132.ibm.com/webapp/wcs/stores/servlet/ProductDisplay?productId=8595139&storeId=1&langId=-1&catalogId=-840


I can understand the drive not being able to use all 160GB of space because that relies on compression and the amount of space saved due to compression varies depending on the data.

The problem here is that the tape isn't even storing its native uncompressed capacity. 56GB is a lot short of 80GB.

Without any compression involved the drive should be able to store 80GB worth of space. That is what is being advertised and what we bought it to do.
.

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