On 10/06/2011 10:36 PM, Kshitij Mehta wrote:
Hello,
I have a pvfs2 file system configured over 20 IO servers with a
default stripe size of 64Kbytes.
I am running a simple test program where I write a matrix to file.
This is what I see:
If the 1GByte matrix is written in block sizes of 2Mbytes, the
performance is much better than writing the matrix in blocks of
64Kbytes. I am not sure I understand why. Since the stripe size is
64KB, every block of 2MB eventually gets broken into 64KB blocks which
are written to the IO servers, so the performance should nearly be
equal. I would understand why writing block size < stripe_size should
perform badly, but when the block size exceeds the stripe size, I
expect the performance to peak out.
Can someone explain what happens here? Your help is appreciated.
I can't explain only confirm. I also did some test with following results.
with pvfs2-cp
18.18
over pvfs2fuse
dd blocksize MB/s
4k 4.4
8k 6.3
16k 7.3
32k 8.8
64k 9.9
128k 18.7
256k 18.7
512k 18.8
1024k 18.8
2048k 18.8
over pvfs2fuse
cp 8.2
rsync 14.8
over nfs
cp 10.6
rsync 11.0
Further earlier was/is mentioned that ongoing effort is put in
optimizing pvfs2/orangefs with small file-sizes. So AFAIK it is by
design, but not knowing the reasoning behind it.
Best,
Kshitij Mehta
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