9.1-stable: ATI IXP600 AHCI: CAM timeout

[Oliver Fromme]

Now I have some more information ...

The problem disappears when I disable NCQ, i.e. set the
number of tags to 1 with camcontrol.  Using binary search
I found out that the problem also disappears with 2 tags,
but with 3 tags I get the same amout of errors as with
the default of 32 tags.

Interestingly, the problems also disappears when I reduce
the SATA level from II to I (i.e. from 3 to 1.5 Gbit/s),
even if the NCQ tags are left at the default of 32.

Now the question is:  Is it better to reduce the NCQ tags
from 32 to 2, or to reduce the SATA bandwidth from 3 Gbps
to 1.5 Gbps?  What is more likely to impact performance
on a mixed server with shell users, apache, sendmail, DNS
and a few other things?

Best regards
   Oliver


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