Date: Fri, 21 Jan 2005 08:31:06 -0800 From: "Kevin Oberman" <oberman@es.net> To: Mark Kirkwood <markir@paradise.net.nz> Cc: "Jim C. Nasby" <decibel@decibel.org> Subject: Re: Disabling write-behind on IDE drives, and SMART Message-ID: <20050121163106.B01855D08@ptavv.es.net> In-Reply-To: Your message of "Fri, 21 Jan 2005 20:53:12 %2B1300." <41F0B4E8.9090507@paradise.net.nz>
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> Date: Fri, 21 Jan 2005 20:53:12 +1300 > From: Mark Kirkwood <markir@paradise.net.nz> > Sender: owner-freebsd-stable@freebsd.org > > Jim C. Nasby wrote: > > Question one: how do I disable write caching on IDE drives? I know the > > setting is hw.ata.wc=0, but where do I put that? In loader.conf? This is > > FreeBSD 4.10, btw. > > > In /boot/loader.conf will do it. > > > Also, has any thought been given to making the default 0, like it is for > > SCSI devices? I'm honestly surprised and disappointed that the default > > is speed over data integrity. > I think it was trialled in 4.3 then changed for 4.4 (according to the > handbook, the performance hit was considered to be too high) Having been involved in the 4.x flip-flop, the performance cost on some systems can be HUGE! Backing up my laptop (40 GB) went from 40 minutes to five hours when the write cache was turned off. On the other hand, it is a real risk, especially when combined with softupdates. For servers that lack solid backup power (not a 10 minute UPS), I would probably turn it off. But for most systems it is probably worth the risks. -- R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: oberman@es.net Phone: +1 510 486-8634
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