Doug McNaught wrote:
Kevin Barnard <[EMAIL PROTECTED]> writes:
Actually you are both are right and wrong. The XRaid uses
FibreChannel to communicate to the host machine(s). The Raid
controller is a FibreChannel controller. After that there is a
FibreChannel to UltraATA conversion for each drive, separate ATA bus
for each drive.
What I am curious about is if this setup gets around ATA fsync
problems, where the drive reports the write before it is actually
performed.
Good point.
(a) The FC<->ATA unit hopefully has a battery-backed cache, which
would make the whole thing more robust against power loss.
(b) Since Apple is the vendor for the drive units, they can buy ATA
drives that don't lie about cache flushes. Whether they do or not
is definitely a question. ;)
FYI: http://developer.apple.com/technotes/tn/pdf/tn1040.pdf a tech note on write cache flushing.
A bit dated now, but perhaps some other tech note from Apple has more recent information.
-- Alan
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