I've been following the thread about disk data consistency with some interest. Given that many IDE disk drives may choose to hold data in their write buffers before actually writing it to disk, and given that the ordering of the writes may not be the same as the OS or application expects, the only obvious way I can see to overcome this, and ensure the data is truly written to the physical platters without disabling write caching is to overwhelm the disk drive with more data than can fit in its internal write buffer.
So, if you have an IDE disk with an 8Mb cache, guess what, send it an 8Mb chunk of random data to write out when you do an fsync(). Better still, locate this 8Mb as close to the middle of the travel of its heads, so that performance is not affected any more than necessary. If the drive firmware uses a LILO or LRU policy to determine when to do its disk writes, overwhelming its buffers should ensure that the actual data you sent to it gets written out Of course, guessing the disk drive write buffer size and trying not to kill system I/O performance with all these writes is another question entirely ... sigh !!! Jason _______________________________________________ Qemu-devel mailing list Qemu-devel@nongnu.org http://lists.nongnu.org/mailman/listinfo/qemu-devel
