> > That's not quite what I meant by "trust". Some drives lie about the > > flush. > > Is that really true, or a misdiagnosed software bug? I've yet to find a drive that lies about write completion. (*) The problem is that the drives boot-up default is write-caching enabled (or perhaps the system BIOS sets it that way). If you turn an IDE disks write cache off explicity, using hdparm or similar, they behave. The problem, I think, is a bug in hdparm or the linux kernel: if you use the little-'i' option, the output indicates the WC is disabled. However, if you use big-'I' to actually interrogate the drive, you get the correct setting. I tested this a while ago by writing a program that did fsync() to test write latency and random-reads to test read latency, and then comparing them. - Guy * I did experience a too-close-to-call case, where after write-cache was disabled, the write latency was the same as the read latency. For every other drive the write latency much, MUCH higher. However, before I disabled the WC, the write latency was a fraction of the read latency.
