Re: Anyone familiar with Apple Xserve RAID

Doug McNaught wrote:

>Kevin Barnard <kbarnard(at)speedfc(dot)com> 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