scsi tape issue

terrywalters · 10-04-2017, 08:05 PM

Hi everyone,

My first post so probably in the wrong forum.

I need to be able to read large blocks, 2 megabyte plus, from a scsi tape drive. I always get an error.

I've been told that it might be the scatter/gather limitations in the st.c driver but it is set to 256.

Does anyone know where I might research this? All my google searches have been to no avail.

Thanks,
Terry Walters

jefro · 10-04-2017, 09:07 PM

Hello and welcome to LQ.

You will need to offer a bit more information.

Did it ever work?
What command are you using?
How old is this stuff?
What is the error?

Thoughts.
https://linux.die.net/man/4/st
https://www.cyberciti.biz/faq/rhel-c...ape-blocksize/ however think it's different in modern linux.

michaelk · 10-04-2017, 10:36 PM

Its been a long time and unfortunately I can not remember, lost the information (house was hit by lightning) but you need to modify the st.c driver to increase the buffer to 2MB blocks and recompile.

I used a device that wrote 1MB blocks to a DLT drive. Its one of the reasons I started using linux because by modifying the source code I could use almost any SCSI card versus windows where there was only one or two cards that the driver was already written for large blocks.

terrywalters · 10-05-2017, 07:01 PM

Turns out the problem was tape drive specific. I was blaming the scsii driver or the hba but the problem changes when I change tape drives.

Turns out each type of tape drive has a maximum block size that it will allow.

Thanks for your thoughts, they did make me think enough to find the answer.