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. > > _______________________________________________ > freebsd-current_at_freebsd.org <mailto:freebsd-current_at_freebsd.org> mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-current <https://lists.freebsd.org/mailman/listinfo/freebsd-current> > To unsubscribe, send any mail to "freebsd-current-unsubscribe_at_freebsd.org <mailto:freebsd-current-unsubscribe_at_freebsd.org>"Received on Thu Jun 08 2017 - 16:46:31 UTC
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