Vladislav Bolkhovitin wrote:
Bart Van Assche wrote:
[...]
I can run disktest on the same setups I ran dd on. This will take some
time however.
Disktest was already referenced in the beginning of the performance
comparison thread, but its results are not very interesting if we are
going to find out, which implementation is more effective, because in
the modes, in which usually people run this utility, it produces latency
insensitive workload (multiple threads working in parallel). So, such
There are other issues with disktest, in that you can easily specify
option combinations that generate apparently 5+ GB/s of IO, though
actual traffic over the link to storage is very low. Caveat disktest
emptor.
multithreaded disktests results will be different between STGT and SCST
only if STGT's implementation will get target CPU bound. If CPU on the
target is powerful enough, even extra busy loops in the STGT or SCST hot
path code will change nothing.
Additionally, multithreaded disktest over RAM disk is a good example of
a synthetic benchmark, which has almost no relation with real life
workloads. But people like it, because it produces nice looking results.
I agree. The backing store should be a disk for it to have meaning,
though please note my caveat above.
Actually, I don't know what kind of conclusions it is possible to make
from disktest's results (maybe only how throughput gets bigger or slower
with increasing number of threads?), it's a good stress test tool, but
not more.
Unfortunately, I agree. Bonnie++, dd tests, and a few others seem to
bear far closer to "real world" tests than disktest and iozone, the
latter of which does more to test the speed of RAM cache and system call
performance than actual IO.
Disktest is new to me -- any hints with regard to suitable
combinations of command line parameters are welcome. The most recent
version I could find on http://ltp.sourceforge.net/ is ltp-20071231.
Bart Van Assche.
Here is what I have run:
disktest -K 8 -B 256k -I F -N 20000000 -P A -w /big/file
disktest -K 8 -B 64k -I F -N 20000000 -P A -w /big/file
disktest -K 8 -B 1k -I B -N 2000000 -P A /dev/sdb2
and many others.
Joe
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