Date: Tue, 7 Dec 1999 00:29:12 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Julian Elischer <julian@whistle.com> Cc: Mike Smith <msmith@FreeBSD.ORG>, cvs-committers@FreeBSD.ORG, cvs-all@FreeBSD.ORG Subject: Re: cvs commit: src/sys/kern kern_shutdown.c Message-ID: <199912070829.AAA75674@apollo.backplane.com> References: <Pine.BSF.4.10.9912062159300.20503-100000@current1.whistle.com>
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:Softupdates is pointless without this because Soft Updates cannot
:guarantee the state of the filesystem to be sane unless the disk does not
:lie about whether it has written to the disk. Soft updates also makes all
:the writes async, so who cares.. :-)
:
:More precisely, the order of the writes must be absolutly maintained
:and disks that buffer writes usually reserve the right to re-order
:adjacent writes.
:
:This is basically what we decided was needed in discussion with Kirk to
:make Soft Updates safe. (The whole point).
:
:Julian
The disk can lie about whether it has written data to the disk without
messing softupdates up, but it cannot reorder writes that the system has
told it must be ordered. SCSI has a tag to guarentee ordering (or not),
but I don't know if IDE has the same sort of feature.
-Matt
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