Date: Sat, 3 Oct 1998 11:24:50 +1000 From: Bruce Evans <bde@zeta.org.au> To: Don.Lewis@tsc.tdk.com, gibbs@plutotech.com Cc: freebsd-fs@FreeBSD.ORG, freebsd-scsi@FreeBSD.ORG Subject: Re: filesystem safety and SCSI disk write caching Message-ID: <199810030124.LAA18635@godzilla.zeta.org.au>
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>>BTW, with softupdates, and tagged command queuing enabled in CAM, there >>is not much of a performance hit from turning off write caching. I >>saw "make buildworld" increase from about 2 hours to 2 hours 5 minutes, >>and "make -j6 buildworld" increase from about 1 hour 30 minutes to >>1 hour 35 minutes. > >In this particular benchmark, perhaps not, but make buildworld is not >indicative of most I/O loads. I think it can be interpreted as showing that the performance hit is very large. `make world' is mostly cpu-bound, and most of it's i/o's are reads (60% here). I guess it spends less than 5 minutes of its time writing (27000 block output operations here). An increase of 5 minutes is very large. Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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