Re: write cache on usb disks and zfs

Thanks for the reply.

This was exactly what I was after, many thanks.  Once I've sorted through my 
various usb caddies, I'll submit a similar PR.


regards

Duncan

On Sun, 9 Mar 2008 10:45:22 pm Ben Stuyts wrote:
> Hi,
>
> On 9 Mar 2008, at 06:25, Duncan Young wrote:
> > I am trying to use the USB drives for backup and would like to use
> > zfs on
> > them, but the problem I have is with the cache disabled, I get lots of
> >
> > kernel: (da2:umass-sim0:0:0:0): SYNCHRONIZE CACHE. CDB: 35 0 0 0 0 0
> > 0 0 0 0
> > kernel: (da2:umass-sim0:0:0:0): CAM Status: SCSI Status Error
> > kernel: (da2:umass-sim0:0:0:0): SCSI Status: Check Condition
> > kernel: (da2:umass-sim0:0:0:0): ILLEGAL REQUEST asc:20,0
> > kernel: (da2:umass-sim0:0:0:0): Invalid command operation code
> > kernel: (da2:umass-sim0:0:0:0): Unretryable error
> >
> > errors in /var/log/messages.
> >
> > I am assuming that the error messages are harmless, but it would be
> > nice for
> > zfs to pay attention and not continually issue the commands.  Is
> > there a way
> > to do this?
>
> I had exactly the same problem (on 7-stable) and have added a quirk
> for this particular drive to scsi_da.c. In my case the drive became
> unresponsive for a few seconds, so the transfer rate was very low.
>
> Works fine so far with the quirk. I have filed a PR where you can see
> my changes: http://www.freebsd.org/cgi/query-pr.cgi?pr=121474
>
> Ben