>> It appears all that was done was to make the start routines not use
>> SCSI_NOSLEEP when called from the strategy routine.  It is still set
>> when called from an interrupt (i.e. on command completion), so if you
>> have enough I/O pending to overflow the SCBs already allocated, you
>> will still lose.  This is made more noticable by ccd because it can
>> have the effect of queueing many requests at once to the same
>> controller.
>
>Well, I guess this is true, but in my case, two disks of the four
>caused the problem while two of them worked OK.  Even the same kind
>of disks fail / work, depending on the firmware version.  Maybe there's
>something else that's not working right in the ahe driver?

Are you sure that it is only two specific disks?  Since you are not
using tagged queueing, each drive that is active will consume two
SCBs out of the 4 that the 2742 supports.  So long as you run only
two drives at once, you should never see this error.  As soon
as you start using a third drive, you should start seeing this error.

>What are the SCBs, btw?  Some limited resource of the SCSI interface
>or something in the kernel or..?

SCSI Command Block.  An SCB contains all the information that the
controller requires to complete a command.  The 2742 can only store
4 of them in its local memeory at once.

>
>  -jm
>

--
Justin T. Gibbs
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  FreeBSD: Turning PCs into workstations
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