backup tape problem

[kholikt]

We have a server that contains around 17GB of data. Currently, we are trying to backup the server using a DDS3 tape. However, the tape drive will backup up to 16GB only and it will actually required for second tape. We are using Omniback to start the backup.

The tape has been reinitialized to 24GB before use. My question here is what could be the possible cause that omniback required two tapes instead of one?

Is this possible that the tape drive is faulty. By the way, DDS3 theoriticaly should be able to handle around 24GB kind of capacity with compression on.

Any help will appreciated

[Patrick Wallek]

What type of data are you backing up? If the data is not very compressable then you will not get the full 24 GB of data on the tape.

DDS3 tapes are rated for 12GB native and 24GB assuming a 2:1 compression ratio. If the data you are writing to tape is not very compressable, like some pictures, video, already compressed file, etc., then you may very well only get 12 GB of data on the tape. 16GB is saying the you are getting a 1.25:1 compression ratio. That is extremely possible. You probably aren't doing anything wrong.

If you must get all the data on a single tape, then look at a DDS4 drive. DDS4 is rated at 20GB native and 40GB with 2:1 compression. The tape is a 150 meter (I think) tape.

[kholikt]

I am using a C 1537A tape drive...as I can't find the manual from hp web site. Is that possible that this drive itself is only DDS2 capable.

[Alexander M. Ermes]

Hi there.
That tape drive is only DDS2.
Sorry.
Alexander M. Ermes

[John Waller]

If the drive is accepting DDS3 tapes it can't be a DDS2 drive has drives are backward compatible but a DDS2 can not accept a DDS3 tape.
You need to be aware that 24Gb assumes 2:1 compression. With some database's and applications you can't get 2:1 so you can't get 24Gb on a DDS3 tape.

[Joseph C. Denman]

I agree with John. If it were a DDS2 drive, it would not accept the DDS3 tape. I would have to assume the data is not very compressable and the 16GB is all you are going to be able to fit on a tape. DDS3 tapes are 12GB native, so at least you are getting some compression.

...jcd...

[Carlos Fernandez Riera]

There is a lot of literature about tapes, compresion and other factors affecting capacity on the forum.

try to search about these topics.

Regards.

[Robert Broadley]

What you are reporting as a 1537a tape drive is actually the inquiry string for a number of DDS-3 (DAT 24) drives including the C155a, C1555 and C1556 families. See http://www.hp.com/cposupport/information_storage/support_doc/lpg50124.html for more information.

[Steve Labar]

What tape length are you using? Have you confirmed that your tape length has 24GB capacity?

Steve