Re: Double buffered cp(1)

[Dan Nelson]

In the last episode (Apr 26), Kent Stewart said:
> I just noticed that mine isn't showing "Tagged Queueing Enabled" is
> that something I can set? The adapter is an Adaptec 2940uw.
> 
> da0 at ahc0 bus 0 target 4 lun 0
> da0: <IBM DCAS-34330W S65A> Fixed Direct Access SCSI-2 device
> da0: 40.000MB/s transfers (20.000MHz, offset 8, 16bit)
> da0: 4134MB (8467200 512 byte sectors: 255H 63S/T 527C)

The CAM code has a quirk entry for IBM DCAS drives that turns it off;
check out /sys/cam/cam_xpt.c, line 320.  I suggest benchmarking with
and without the quirk entry, and if it's faster with tagged queueing,
update PR kern/10398.

-- 
        Dan Nelson
        [EMAIL PROTECTED]


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