I've replaced my backup server and I switched from a Debian Stretch to a CentOS7. I have a SuperLoader 3 LTO4 SCSI on an old adaptec SCSI 160. At first, I had to use the CentOSplus kernel which add the old SCSI aic7xxx module to have my hardware detected.
It's working, but I have a top speed to 2MB/s while I do a "btape speed" test.
I've also tried with another SCSI controller 320; this one is natively supported by the CentOS kernel. Same issue; I tried to boot Debian on the same hardware and at this moment, I get the max speed.
Right now, I'm pretty sure it's a kernel issue. Do you know if there're any settings to avoid this issue?
Edit 17/04/18 : On tapestat i see i have a 99% write time wait, is it why it's so slow ? Any idea ? I'm starting to lose hope :(