Re: geom_journal - bio_flush not supported on disks connected via usb?

On Mon, 30 Jul 2007 21:12:50 +0200
Pawel Jakub Dawidek <pjd_at_FreeBSD.org> wrote:

> On Mon, Jul 30, 2007 at 03:58:02PM +0200, Marc UBM Bocklet wrote:
> > 
> > Hiho! :-)
> > 
> > 
> > During startup, I got this error (only once):
> > 
> > 
> > GEOM_JOURNAL: Journal 1159150689: da0 contains data.
> > GEOM_JOURNAL: Journal 1159150689: da0 contains journal.
> > GEOM_JOURNAL: Journal da0 clean.
> > (da0:umass-sim0:0:0:0): SYNCHRONIZE CACHE. CDB: 35 0 0 0 0 0 0 0 0
> > 0 (da0:umass-sim0:0:0:0): CAM Status: SCSI Status Error
> > (da0:umass-sim0:0:0:0): SCSI Status: Check Condition
> > (da0:umass-sim0:0:0:0): ILLEGAL REQUEST asc:20,0
> > (da0:umass-sim0:0:0:0): Invalid command operation code
> > (da0:umass-sim0:0:0:0): Unretryable error
> > GEOM_JOURNAL: BIO_FLUSH not supported by da0.
> > 
> > 
> > da0 is 250GB usb disk (using ehci(4)).
> > 
> > I do not understand completely what this means. Has the BIO_FLUSH
> > command only failed once and works now on subsequent tries?
> 
> No, it means that gjournal tried it once and now knows that it's not
> supported, so won't spam you console again.
> 
> > Does BIO_FLUSH never work, because it's not implemented (or can't be
> > implemented) for disks connected via usb? And if thats the case,
> > will that affect geom_journal in any way? Is my data still being
> > journalled correctly? :-)
> 
> If write cache is turned on on your disk, there can be a problem in
> case of a power failure. I don't know how write cache is beeing
> turned on for a disk connected via USB. Is it turned on by default?
> If it's turned off by default, then you are safe.

Thanks a lot for your quick response.

It seems to be disabled by default (thats what the da(4) manpage says):

root_at_ubm:/usr/home/sheep# camcontrol modepage da0 -m 8
IC:  0
ABPF:  0
CAP:  1
DISC:  0
SIZE:  1
WCE:  0
MF:  0
RCD:  0
Demand Retention Priority:  0
Write Retention Priority:  1
Disable Pre-fetch Transfer Length:  0
Minimum Pre-fetch:  44
Maximum Pre-fetch:  58303
Maximum Pre-fetch Ceiling:  48902


The only remaining question is, if the write cache for a disk connected
via USB is really affected by this setting (since da0 is just a "fake"
scsi disk, as I understand it). Can someone comment on that?


Bye
Marc

-- 

"Come away, O human child!
To the waters and the wild
With a faery, hand in hand,
For the world's more full of weeping than you can understand."

W.B. Yeats, The Stolen Child