Date: Sat, 6 Dec 2003 18:39:52 -0800 (PST) From: Don Lewis <truckman@FreeBSD.org> To: nate@root.org Cc: freebsd-scsi@FreeBSD.org Subject: Re: More Adaptec 29320 + Seagate ST336607LW woes Message-ID: <200312070239.hB72dqeF043314@gw.catspoiler.org> In-Reply-To: <20031206164352.K33312@root.org>
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On 6 Dec, Nate Lawson wrote: > On Sat, 6 Dec 2003, Don Lewis wrote: >> One place where folks have noticed a performance difference between WCE >> on and WCE off is when using newfs after we got rid of the buffered >> block devices and forced newfs to use the raw character device. Newfs >> only issues one write() at a time and waits for the status before >> issuing another write(). If WCE is on, the writes only have to hit the >> drive cache before the drive returns a status that gets returned to >> userland, but if WCE is off the data has to hit the platter before the >> status is returned, which slows down newfs quite considerably. Tagged >> queuing doesn't make any difference in this case because the drive will >> only see at most only one command at a time. > > Great explanation. We should probably add write clustering to newfs at > some point. Yes, but it is somewhat less of an issue now that UFS2 does lazy inode initialization.
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