On Mon, 13 Nov 2006, Guy Thornley wrote:
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.
I found a rather ominous warning from SGI on this subject at http://oss.sgi.com/projects/xfs/faq.html#wcache_query
"[Disabling the write cache] is kept persistent for a SCSI disk. However, for a SATA/PATA disk this needs to be done after every reset as it will reset back to the default of the write cache enabled. And a reset can happen after reboot or on error recovery of the drive. This makes it rather difficult to guarantee that the write cache is maintained as disabled."
As I've been learning more about this subject recently, I've become increasingly queasy about using IDE drives for databases unless they're hooked up to a high-end (S|P)ATA controller. As far as I know the BIOS doesn't mess with the write caches, it's strictly that the drives default to having them on. Some manufacturers lets you adjust the default, which should prevent the behavior SGI warns about from happening; Hitachi's "Feature Tool" at http://www.hitachigst.com/hdd/support/download.htm is one example I've used successfully before.
-- * Greg Smith gsmith@xxxxxxxxxxxxx http://www.gregsmith.com Baltimore, MD
