Date: Sun, 4 Oct 1998 03:55:51 +0000 (GMT) From: Terry Lambert <tlambert@primenet.com> To: julian@whistle.com (Julian Elischer) Cc: gibbs@plutotech.com, Don.Lewis@tsc.tdk.com, current@FreeBSD.ORG Subject: Re: Softupdates, filesystem safety and SCSI disk write caching Message-ID: <199810040355.UAA24036@usr06.primenet.com> In-Reply-To: <Pine.BSF.3.95.981002135812.15828E-100000@current1.whistle.com> from "Julian Elischer" at Oct 2, 98 02:22:01 pm
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> No this is not what softupdates expects.. > > It expects that data blocks are written before metadata blocks. > (for writing files) > > An example of some of the dependencies for writing a file B are: > > directory blocks depend on > inode blocks, which depend on > indirect blocks, which depend on > datablocks I think it is important to interject something here: Not only does soft updates protect the filesystem integrity by way of ordering metadata, it *also* protects user data integrity. This is *more* than the standard "no options" mount used to do; it is closer to what a "sync" mount does. Again, in English: soft updates is *better* than sync metadata with async data. The ability to protect user data was why I was initially so adamant about a generic implementation of a dependency graph event reconciliation registration mechanism. If I could register a new dependency type called "transaction", I could export a transactioning interface to user space. A transaction, in this sense, is an implied relationship between two or more files data contents. As it is, I can use the old fashioned technique, and do fsync() calls; this is, however, not nearly so satisfying. 8-(. > This is not acceptable to softupdates. (as defined by McKusick, Ganger and > Pratt) Uh, "Patt". 8-). Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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