In the last episode (Sep 21), Christoph Kukulies said:
Just FYI, don't know whether I should bother but since the recent
upgrade to -current (aout) I'm seeing the following log messages:
Sep 21 20:35:58 blues /kernel: (da0:ncr0:0:0:0): tagged openings now 15
That just means your drive can't handle more than 15 tagged commands at
once. CAM's max is 64 (is there any way to raise this?), so the first
time your system hits the disk heavily, your drive will complain about
the number of tags it can't handle, and the kernel message will pop up.
You can adjust the maximum by adjusting the default quirk entry in
cam_xpt.c or by putting in a specific quirk entry for your device that sets
the limit higher. Most drives don't have any more than 64 tags. I think
there are some external RAID controllers that may have more.
There's no way to query the drive for this information (as far as I
know), so the system basically tries to use as many tagged commands as
possible until the drive complains.
Although some drives, like the Atlas II, will keep returning queue full
until we've reduced the number of tags to 0. That's why we've got quirk
entries that set the lower limit for those drives to 24.
Some of Netware's SCSI drivers print the same messages. It's actually
nice to see the message; then I know what drives not to buy next time
Yep. Many (most?) of the better Seagates handle 63 tags. My IBM Ultrastar
9ZX has 64.