Date: Tue, 13 Mar 2001 07:45:55 -0500 (EST) From: Peter Dufault <dufault@hda.hda.com> To: Alfred Perlstein <bright@wintelcom.net> Cc: mobile@freebsd.org, stable@freebsd.org Subject: Re: Disk I/O problem in 4.3-BETA Message-ID: <200103131245.f2DCjuB22590@hda.hda.com> In-Reply-To: <20010313035755.S29888@fw.wintelcom.net> from Alfred Perlstein at "Mar 13, 2001 03:57:55 am"
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> * Pete French <pfrench@firstcallgroup.co.uk> [010313 03:51] wrote: > > All very interesting, but a small point has been forgotten > > hasnt it ? The way I read this thread is that until recentlly > > write-caching was enabled by default and has now been disabled (hence > > the original obseravtion of disc performance dropping). > > > > I havent noticed that FreeBSD has a bad reputation for loss of data > > in the event of am power outage, and my own experience backs this up. > > As so many people appear to have been running it this way by default until > > now you might have though that if it were a serious problem in reality then > > people would have noticed by now ? > > Your optimism is appreciated, however just because you can't see > the approaching hordes doesn't mean they're not at the gates. > > To be true to our users, we need to either: > > 1) turn off write caching. > 2) propogate bwrite() intention down to the device layer. I haven't been following this too closely, but if "2)" means use ordering commands to the drive firmware to ensure block ordering you need a warning about using an UPS and being nervous about disk firmware revs. I think write cache enable with an UPS and SCSI drives that grew up in a workstation environment is safe, now with either mass-market drives or counting on block ordering firmware working properly I get nervous too, and with soft updates reducing the disk overhead maybe it just isn't worth it. Peter -- Peter Dufault (dufault@hda.com) Realtime development, Machine control, HD Associates, Inc. Fail-Safe systems, Agency approval To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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