Hi Rick, Thanks for your suggestion. We made the changes accordingly. That said, by default, sd(7D) will do RMW to misaligned I/O with warning message. Custormers can configure the behavior as do RMW without warning message and do not do RMW with error returned. The configuration will be per device based (PSARC 2008/465 [s]sd-config-list). We don't have a mechanism to configure the behavior per partition based.
I attached the modified rmw design doc. Thanks, Larry Rick Matthews ??: > Project team, > > My remaining issues for this project are all centered around > the read-modify-write (RMW) proposal of your project. My primary > concern is the default state of RMW as an error. My concerns are > that an error return by default is inappropriate. I understand > the concerns of the project that serious performance concerns > may go undetected without the error return by default. Array > manufacturers also are subject to this penalty, if the physical > I/O is mis-aligned. The default behavior for arrays does not > appear to be a fatal error. > > An alternate proposal would be a "multi-state" RMW flag. > I'd propose a "warning only" mode as the default, and > "return error on RMW" and "do not report RMW conditions" > as other potential settings. > > Having this state be a "global" setting would also seem to > be overdone. A system-wide setting seems too much, and a "per-disk" > setting also seems the wrong granularity. Setting this on a > "per disk partition" would seem to be adequate. Having a global > that takes precedence over the per partition would also be > acceptable, in my opinion. > > Please consider these issues. > -------------- next part -------------- An embedded and charset-unspecified text was scrubbed... Name: rmw_design_new.txt URL: <http://mail.opensolaris.org/pipermail/opensolaris-arc/attachments/20090316/e558ffe5/attachment.txt>
