Date: Tue, 15 Apr 2003 20:37:47 +0200 From: Marko Zec <zec@tel.fer.hr> To: Kirk McKusick <mckusick@beastie.mckusick.com> Cc: freebsd-stable@freebsd.org Subject: Re: PATCH: Forcible delaying of UFS (soft)updates Message-ID: <3E9C517B.6039679A@tel.fer.hr> References: <200304130004.h3D04Vb5006635@beastie.mckusick.com>
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Kirk McKusick wrote: > I am of the opinion that fsync should work. Applications like > `vi' use fsync to ensure that the write of the new file is on > stable store before removing the old copy. If that semantic > is broken, it would be possible to have neither the old nor > the new copy of your file after a crash. I do not consider > that acceptable behavior. Further, the fsync call is used > to ensure that link/unlink/rename have been completed. So > more than just fsync is being affected by your change. Lastly, > I often write out a file when I am about to suspend my laptop > (for low battery or other reasons) and I really want that file > on the disk now. I do not want to have to wait for it to decide > at some future time to spin up the disk. > > I suggest that you make the disabling of fsync a separate > option from the rest of your change so that people can > decide for themselves whether they want partial savings > with working semantics, or greater savings with broken > semantics. I am also intrigued by the changes proposed by > Ian Dowse that may better accomplish the same goals with > less breakage. Tempted by a lot of opposition to the concept of (optionally) ignoring fsync() calls when running on battery power, I wonder what effect the concept of unconditional delaying of _all_ disk updates by ATA-disk firmware will make on FS consistency in case of system crash or power failure? I do not want to imply such a concept is a priori bad, however I fail to realize its advantages over OS-controlled delaying of disk synching. Marko
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