On Sun, 28 Jun 2009, Bob Friesenhahn wrote:
On Sun, 28 Jun 2009, Bob Friesenhahn wrote:
Today I experimented with doubling this value to 688128 and was happy to
see a large increase in sequential read performance from my ZFS pool which
is based on six mirrors vdevs. Sequential read performance jumped from
552787 MB/s to 799626 MB/s. It seems that the default driver buffer size
interfers with zfs's ability to double the read performance by balancing
the reads from the mirror devices. Now the read performance is almost 2X
the write performance.
Grumble. This may be a bit of a red herring.
Perhaps this Emulex tunable was not entirely a red herring.
Doubling the default for this tunable made a difference to my
application. It dropped total real execution time from 2:45:03.152 to
2:24:25.675. That is a pretty large improvement.
If I run two copies of my application at once and divide up the work,
the execution time is 1:42:32.42. Even with two (or three) copies of
the application running, it seems that zfs is still the bottleneck
since the square-wave of system CPU utilization becomes even more
prominent, indicating that all readers are blocked during the TXG
sync.
Bob
--
Bob Friesenhahn
bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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