Hello,
As I mentioned a while ago to Pete on the low performance of a joined file,
I provided a little demo of the problem at the end. The impression I have
got from various tests is that a file created by joining multiple files
together can bring read/write performance to very low.
Anybody would like to pose a speculation on where the problem could lie in?
Thanks,
Weikuan
P.S.: jaguar5 is a login node, just a regular linux client. I have also
tested the same on a linux clueter, only 80MB/sec read/write bandwidth was
seen on a joined file across 20 SATA targets, while the aggregated bandwidth
is more than 1000MB/sec.
# Create four different files each with stripe_count 4
[EMAIL PROTECTED] wyu]$ lfs setstripe /tmp/join/file.01 1048576 1 4
[EMAIL PROTECTED] wyu]$ lfs setstripe /tmp/join/file.02 1048576 5 4
[EMAIL PROTECTED] wyu]$ lfs setstripe /tmp/join/file.03 1048576 9 4
[EMAIL PROTECTED] wyu]$ lfs setstripe /tmp/join/file.04 1048576 13 4
[EMAIL PROTECTED] wyu]$ time dd if=/dev/zero of=/tmp/join/file.01 count=65536
[EMAIL PROTECTED] wyu]$ time dd if=/dev/zero of=/tmp/join/file.02 count=65536
[EMAIL PROTECTED] wyu]$ time dd if=/dev/zero of=/tmp/join/file.03 count=65536
[EMAIL PROTECTED] wyu]$ time dd if=/dev/zero of=/tmp/join/file.04 count=65536
# join them together
[EMAIL PROTECTED] wyu]$ lfs join /tmp/join/file.01 /tmp/join/file.02
[EMAIL PROTECTED] wyu]$ lfs join /tmp/join/file.01 /tmp/join/file.03
[EMAIL PROTECTED] wyu]$ lfs join /tmp/join/file.01 /tmp/join/file.04
# create two other file with stripe count 4 and 16
[EMAIL PROTECTED] wyu]$ lfs setstripe /tmp/join/file.05 1048576 1 4
[EMAIL PROTECTED] wyu]$ lfs setstripe /tmp/join/file.06 1048576 2 16
# Demo of the low write performance
[EMAIL PROTECTED] wyu]$ time dd if=/dev/zero of=/tmp/join/file.01 count=262144
262144+0 records in
262144+0 records out
real 0m42.059s
user 0m0.107s
sys 0m36.880s
[EMAIL PROTECTED] wyu]$ time dd if=/dev/zero of=/tmp/join/file.05 count=262144
262144+0 records in
262144+0 records out
real 0m11.002s
user 0m0.092s
sys 0m10.821s
[EMAIL PROTECTED] wyu]$ time dd if=/dev/zero of=/tmp/join/file.06 count=262144
262144+0 records in
262144+0 records out
real 0m14.650s
user 0m0.074s
sys 0m14.487s
# Demo of the low read performance
[EMAIL PROTECTED] wyu]$ time dd of=/dev/zero if=/tmp/join/file.01 count=262144
262144+0 records in
262144+0 records out
real 0m54.099s
user 0m0.074s
sys 0m53.622s
[EMAIL PROTECTED] wyu]$ time dd of=/dev/zero if=/tmp/join/file.05 count=262144
262144+0 records in
262144+0 records out
real 0m15.435s
user 0m0.053s
sys 0m15.355s
[EMAIL PROTECTED] wyu]$ time dd of=/dev/zero if=/tmp/join/file.06 count=262144
262144+0 records in
262144+0 records out
real 0m18.642s
user 0m0.067s
sys 0m18.528s
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