Trying to pass a tape-changer through to a RHEL6 VM isn't working, not sure why.
1) I had to write custom udev rules to ensure I was always passing through the correct SCSI devices, enumeration doesn't seem to be entirely stable or deterministic on my system.
2) I had to forcibly disable the st and ch modules on the host, otherwise udev kept trying to kill the "modprobe" command because it was taking too long (a full Dell PV-124T autoloader takes ~5 minutes to respond to SCSI SUB-UNIT STATUS because it moves each tape past the barcode scanner).
3) I had to modify QemuServer.pm to allow for Type==8 devices (there's a patch floating around on a mailing list that Google found for me)
4) I also had to set cache=writethrough manually in the config file
KVM finally agreed to start once all those things had been done, but the guest VM doesn't see the passed-through devices at all.
I'm continuing to work on it, but does anyone know how to make this ^%$#@! work???
Notes:
-PCIe passthrough doesn't work because the host is just slightly too old to have a working IOMMU (Opteron 2300 series)
-iSCSI doesn't work because of (I think) the SCST module problem, and also because it's just not fast enough: I have 1Gbps network infrastructure, and Ultrium-5 (?) tape drives need to be fed more than 100MBytes/sec to stream properly.
1) I had to write custom udev rules to ensure I was always passing through the correct SCSI devices, enumeration doesn't seem to be entirely stable or deterministic on my system.
2) I had to forcibly disable the st and ch modules on the host, otherwise udev kept trying to kill the "modprobe" command because it was taking too long (a full Dell PV-124T autoloader takes ~5 minutes to respond to SCSI SUB-UNIT STATUS because it moves each tape past the barcode scanner).
3) I had to modify QemuServer.pm to allow for Type==8 devices (there's a patch floating around on a mailing list that Google found for me)
4) I also had to set cache=writethrough manually in the config file
KVM finally agreed to start once all those things had been done, but the guest VM doesn't see the passed-through devices at all.
I'm continuing to work on it, but does anyone know how to make this ^%$#@! work???
Notes:
-PCIe passthrough doesn't work because the host is just slightly too old to have a working IOMMU (Opteron 2300 series)
-iSCSI doesn't work because of (I think) the SCST module problem, and also because it's just not fast enough: I have 1Gbps network infrastructure, and Ultrium-5 (?) tape drives need to be fed more than 100MBytes/sec to stream properly.