First write to a tape drive

[Richard Jordan_1]

I am currently developing an application that writes/reads data to/from an HP DDS DAT40i tape drive, however I think that my problem probably applies to tape drives in general.

As part of our requirements we have to able to show the write/read data rate achieved. All we do is to simply time how long the write takes and from the amount of data written we can calculate the data rate.

However, the problem is that the first write session is always slower than any subsequent writes. This causes a problem for us because the first write fails the requirement.

I suspect that maybe what is happening is the tape mechanism has to get ready, or that the tape performs some seek function before the data is written ?

Does anyone know what actually happens on the first write session and why this is slower. Is there any HP documentation available that explains what is happening within the tape drive.

Thanks, in anticipation.