Jens Axboe wrote:
On Fri, Jul 01 2005, Bryan Henderson wrote:
Wouldn't a commercial class drive that ignores explicit flushes be
infamous? I'm ready to accept that there are SCSI drives that cache
writes in volatile storage by default (but frankly, I'm still skeptical),
but I'm not ready to accept that there are drives out there secretly
ignoring explicit commands to harden data, thus jeopardizing millions of
dollars' worth of data. I'd need more evidence.
I'm pretty sure I have an IBM drive that does so (its flush cache
command is _really_ fast), as a matter of fact :-) I need to locate it
and put it in a test box to re-ensure this.
I'm not sure such drives would necessarily be infamous, hardly anyone
would notice anything wrong in a desktop type machine. Which is what
these drives were made for.
One other thing to keep in mind is that drive firmware can have bugs
just like any other bit of code, so a drive may have a bug in one
firmware revision that gets fixed in a following one.
I am not sure how much that other operating system uses flush cache
commands, but until the write barrier patch, it has been a relatively
rarely issued command for Linux and breakage would not be noticed.
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