It took manufacturers of SCSI drives some years to get this right. Around 1997 or so we were still seeing drives at my former employer that didn't properly flush their caches under all circumstances (and had other "interesting" behaviours WRT caching).
Lots of ATA disks never did bother to implement the write cache controls. I haven't talked recently with any vendors who have been sourcing SATA disks, so I don't know what they're seeing. Generally the major players have their own disk qualification suites and often wind up with custom firmware because they want all of their detected bugs fixed before they'll accept a particular disk. If you buy a disk off-the-shelf, you get a drive that's gone through the disk manufacturer's testing (which is good, don't get me wrong) but hasn't been qualified with the particular commands or configuration that a particular operating system or file system might send. If you can do your own tests, that would be best; but that involves executing a flush (with all the various combinations of commands outstanding, dirty vs. clean cache buffers, etc.) and immediately powering off the device, which generally can't be done without special hardware. My *hunch* is that "enterprise-class" SATA disks have probably gone through more of this sort of testing than consumer SATA, even at the drive manufacturers. (It's not at all the same firmware.) This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
