Re: Time to increase MAXPHYS?

Huh, can't say I've tested that.  I'll try to look into this.  Thanks
for the report!

On 0608T2046, peter.blok_at_bsd4all.org wrote:
> One area that breaks after changing MAXPHYS from 128K to 1MB is the iscsi target. I don’t have details, because that server is semi-production and I reverted it back ASAP
> > On 5 Jun 2017, at 19:49, Edward Tomasz Napierała <trasz_at_FreeBSD.org> wrote:
> > 
> > On 0604T0952, Hans Petter Selasky wrote:
> >> On 06/04/17 09:39, Tomoaki AOKI wrote:
> >>> Hi
> >>> 
> >>> One possibility would be to make it MD build-time OTIONS,
> >>> defaulting 1M on regular systems and 128k on smaller systems.
> >>> 
> >>> Of course I guess making it a tunable (or sysctl) would be best,
> >>> though.
> >>> 
> >> 
> >> Hi,
> >> 
> >> A tunable sysctl would be fine, but beware that commonly used firmware 
> >> out there produced in the millions might hang in a non-recoverable way 
> >> if you exceed their "internal limits". Conditionally lowering this 
> >> definition is fine, but increasing it needs to be carefully verified.
> >> 
> >> For example many USB devices are only tested with OS'es like Windows and 
> >> MacOS and if these have any kind of limitation on the SCSI transfer 
> >> sizes, it is very likely many devices out there do not support any 
> >> larger transfer sizes either.
> > 
> > FWIW, when testing cfiscsi(4) with Windows and OSX I've noticed
> > that both issue 1MB requests.  I wouldn't be surprised if they avoided
> > doing that for older devices, depending on eg the SCSI version reported
> > by device.
> > 
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