On Wed, 2008-05-28 at 15:27 -0400, Justin Piszcz wrote: > > On Wed, 28 May 2008, Chris Snook wrote: > > > Justin Piszcz wrote: > >> > >> > >> On Wed, 28 May 2008, Chris Snook wrote: > >> > >>> Justin Piszcz wrote: > >>>> Hardware: > >>>> > >>> Given that one of the greatest benefits of NCQ/TCQ is with parity RAID, > >>> I'd be fascinated to see how enabling NCQ changes your results. Of > >>> course, you'd want to use a single SATA controller with a known good NCQ > >>> implementation, and hard drives known to not do stupid things like disable > >>> readahead when NCQ is enabled. > >> Only/usually on multi-threaded jobs/tasks, yes? > > > > Generally, yes, but there's caching and readahead at various layers in > > software that can expose the benefit on certain single-threaded workloads as > > well. > > > >> Also, I turn off NCQ on all of my hosts that has it enabled by default > >> because > >> there are many bugs that occur when NCQ is on, they are working on it in > >> the > >> libata layer but IMO it is not safe at all for running SATA disks w/NCQ as > >> with it on I have seen drives drop out of the array (with it off, no > >> problems). > >> > > > > Are you using SATA drives with RAID-optimized firmware? Most SATA > > manufacturers have variants of their drives for a few dollars more that have > > firmware that provides bounded latency for error recovery operations, for > > precisely this reason. > I see--however, as I understood it there were bugs utilizing NCQ in libata? You wouldnt happen to have some more information about this? i havent personally had problems yet, but i havent used it for very long - but since it comes activated by DEFAULT, i would assume it to be relatively stable? > > But FYI-- > In this test, they were regular SATA drives, not special raid-ones (RE2,etc). > > Thanks for the info! > > Justin. > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
