Hi,
What version of MPI are you using? What are the collective buffer sizes
set to? How many aggregators?
Thanks,
Rob
Xinhua Gao wrote:
Hello,
I am using IOR to write/read a shared file with up to 16 processes, each
writing data of 128M in units of 256K. Here is the data I got with
collective IO and independent IO.
# collective IO
#procs write read
2 74.53 12.43
4 36.28 15.85
6 20.66 18.61
8 20.16 23.57
10 22.18 33.15
12 24.18 49.36
# independent IO to a single file
# proc write read (MB/sec)
2 51.98 28.55
4 65.15 55.73
6 83.03 70.01
8 98.96 82.06
10 124.65 102.35
12 126.86 112.36
14 139.63 119.50
16 147.01 154.90
It is a little surprising to see collective IO performance is so low
compared to independent IO. In addition, collective IO does not increase
with increasing number of clients. The set servers has 5 IO servers can
support at least 100MB/sec of IO rates directly from disks.
Anybody can provide some hints? Thanks,
Xinhua
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