On Wed, 20 Oct 2010, Marty Scholes wrote:
Untrue. The performance of a 21-disk raidz3 will be nowhere near the
performance of a 20 disk 2-way mirrror.
You know this stuff better than I do. Assuming no bus/cpu
bottlenecks, a 21 disk raidz3 should provide sequential throughput
of 18 disks and random throughput of 1 disk.
I have some swampland in Florida that you can drain and put a condo
on. If you wait long enough it may become beachfront property. :-)
Before zfs moves on to the next block, it needs to write data to all
the disks and this means that the disks need to line up to the
required position and deposit their load. What you say might be true
in a perfect world. In the real world disks don't perform like
perfect little soldiers and get in mis-step and so the actual
performance is much less than what is theoretically possible. An
extremely well designed and tuned array could support more disks per
vdev.
Bob
--
Bob Friesenhahn
bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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