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Re: Disabling disk caches [Re: CVS commit: src/lib/libc/sys, re sync(1)]
On Mar 26, 2009, at 11:52 AM, David Holland wrote:
On Wed, Mar 25, 2009 at 09:44:52PM +0000, Andrew Doran wrote:
I think we should:
(a) Automatically disable the disk write cache the moment a file
mounted on the disk, unless that file system is known to handle
For our purposes, that leaves logging ffs and zfs (and whatever
modern file systems come along) with the cache enabled.
While technically this may be the right thing, it won't be popular.
(So, why doesn't sync flush the disk write cache?)
Apple went though this exercise a while back and was beaten to a pulp
over slow performance for apps that used fsync().
So now Mac OS X has the F_FULLFSYNC fcntl command which is "fsync() +
flush the disk cache". Apps that require such semantics use it
(b) Change mount to flush the disk cache as a test, if r/w mount.
If we get
an error, send a warning message to the log. This will help us
broken disk drivers fixed.
That seems like a good idea.
David A. Holland
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