Date: Sat, 5 May 2001 17:15:01 -0600 (MDT) From: Doug Russell <drussell@saturn-tech.com> To: Nick Sayer <nsayer@quack.kfu.com> Cc: stable <stable@FreeBSD.ORG> Subject: Re: soft update should be default Message-ID: <Pine.BSF.4.21.0105051703140.95873-100000@beastie.saturn-tech.com> In-Reply-To: <3AF42ACD.5000500@quack.kfu.com>
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On Sat, 5 May 2001, Nick Sayer wrote: > > I still don't totally understand this. In the case of a drive with WCE, > > aren't we always assuming that the drive will correctly write the > > data out eventually, even if the system crashes? > > Yes. But that assumption is flawed. As I said before... In THEORY, in a perfect world. :) My point is... This is a hardware limitation, not something specific to softupdates. I you enable write caching, write some data to the drive, then cut the power before it writes the data, I wouldn't call it softupdates fault. :) > Write caching is evil unless you specifically know that it's being > battery backed. 99.44% of the time, that's not the case. YES! MOST CERTAINLY! Don't get me wrong here. I never enable write caching unless the drive contains scratch data (obj tree, temporary video or audio files, etc.) or if I have both drive power supplies plugged in, with one on a UPS. This isn't so easy on an internal drive, especially and IDE disk. It still isn't softupdates that's the problem, it is that someone's enabling write caching in an environment where it is not safe to do so. Hmmm. This makes me thing of a nifty new product. A small battery system for your hard disks that sits in a drive bay, perhaps. It would be very easy to build some of those. Later...... <Doug> P.S. DEC Storageworks external SCSI chassis are often available from surplus computer dealers for next to nothing. (They only do 40 meg/sec UW). Great for those of us mere mortals who can't afford nice brand new U160 RAID cages. :) I've got three attached to my home workstation right now, and it's the only way I'd even THINK of turning on the WC in any of my drives. I've got about 20 of these, and I know somewhere that had pallets of them last time I was there, if anyone is interested, e-mail me directly and I'll check and see if they have any right now for you. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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