On Aug 21, 2009, at 6:09 PM, Adam Sherman wrote:
On 21-Aug-09, at 21:04 , Richard Elling wrote:
My point is, RAIDZx+1 SHOULD be simple. I don't entirely
understand why it hasn't been implemented. I can only imagine
like so many other things it's because there hasn't been
significant customer demand. Unfortunate if it's as simple as I
believe it is to implement. (No, don't ask me to do it, I put in
my time programming in college and have no desire to do it again :))
You can get in the same ballpark with at least two top-level raidz2
devs and
copies=2. If you have three or more top-level raidz2 vdevs, then
you can even
do better with copies=3 ;-)
Maybe this is noted somewhere, but I did not realize that "copies"
invoked logic that distributed the copies among vdevs? Can you
please provide some pointers about this?
It is hard to describe in words, so I made some pictures :-)
http://blogs.sun.com/relling/entry/zfs_copies_and_data_protection
-- richard
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