On Sat, 11 Aug 2012, Chris Nagele wrote:
So far, running gnu dd with 512b and oflag=sync, the most we can get is 8k
iops on the zil device. I even tried with some SSDs (Crucial M4,
If this is one dd program running, then all you are measuring is
"sequential" IOPS. That is, the next I/O will not start until the
previous one has returned. What you want to test is threaded IOPS
with some number of threads (each one represents a client) running.
You can use iozone to effectively test that.
This command runs with 16 threads and 8k blocks with a 2GB file:
iozone -m -t 16 -T -O -r 8k -o -s 2G
If you 'dd' from /dev/zero then the test is meaningless since zfs is
able to compress zeros. If you 'dd' from /dev/random then the test is
meaningless since the random generator is slow.
Is this the expected result? Should I be pushing for more? In IRC I
was told that I should be able to get 12k no problem. We are running
NFS in a heavily used environment with millions of very small files,
so low latency counts.
Your test method is not valid.
Bob
--
Bob Friesenhahn
bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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