Date: Sat, 19 Sep 1998 20:24:09 +0200 From: Eivind Eklund <eivind@yes.no> To: Terry Lambert <tlambert@primenet.com> Cc: Don.Lewis@tsc.tdk.com, current@FreeBSD.ORG Subject: Re: softupdates & fsck Message-ID: <19980919202409.40703@follo.net> In-Reply-To: <199809191719.KAA10028@usr09.primenet.com>; from Terry Lambert on Sat, Sep 19, 1998 at 05:19:51PM %2B0000 References: <19980919123143.36373@follo.net> <199809191719.KAA10028@usr09.primenet.com>
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On Sat, Sep 19, 1998 at 05:19:51PM +0000, Terry Lambert wrote: > > > That you are seeing these problems implies that the bwrite ordering > > > guarantees that the driver must provide (i.e., that the blocks will > > > be written in the order requested, and that the writes will not > > > return as completed until the data has been committed to the disk) > > > are not being honored. > > > > Given that most drives don't honour these guarantees [1] it may happen > > even without a problem with the driver. > > > > [1] This marks the point where somebody comes runing, waving standards > > documents and becoming more and more red in the face, while I say > > "Yes, I know they say the drives are supposed to - but in fact, the > > drives don't actually *do* what they're supposed to." > > They do if you set their options correctly and insure a holdup > time after power failure, during which you will not engage in > scheduling new writes. Eh? Without an UPS, I can't do that. The problem is drives that don't honour the immediate-write flag, returning before data is committed to disk anyway (done to get better benchmarks). I think there also is some problems with drives that will re-order requests no matter what constraints you give it :-( BTW: I didn't mean that this applied in this particular case, just that this may become a problem when soft updates become fsck-less. Eivind. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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