On Nov 22, 2010, at 11:32 PM, Andrew Deason wrote:
> On Mon, 22 Nov 2010 23:12:57 +0100
> Achim Gsell <[email protected]> wrote:
>
>>>> Trashing? Mmh. I can write 8 1 GB in parallel with dd without
>>>> problems ...
>>>
>>> Are you sure the access pattern for that is the same as the bonnie++
>>> test that's running?
>>
>> OK, here is a simple shell script reproducing the problem:
>
> Er, I'm sorry, I'm not understanding something here. I thought you just
> said that this is _not_ a problem when doing this in parallel with dd.
Yes, and the script is working serial ... the parallel dd's are just an
example, that I don't think it's trashing problem.
1.) This works:
$ for i in 1 2 3 4 5 6 7 8; do dd if=/dev/zero of=file$i bs=1024k count=1024;
done
2.) And this too:
$ for i in 1 2 3 4 5 6 7 8; do dd if=/dev/zero of=file$i bs=1024k count=1024 &
done
3.) But if I first open 8 files and - after this is done - start writing to
these files sequentially, the problem occurs. The difference to 1.) and 2.) is,
that I have these 8 open files while the test is running. This simulates the
"putc-test" of bonnie++ more or less:
fd1 = open("file1");
fd2 = open("file2");
fd3 = open("file3");
fd4 = open("file4");
fd5 = open("file5");
fd6 = open("file6");
fd7 = open("file7");
fd8 = open("file8");
write 1 GB to fd1
write 1 GB to fd2
write 1 GB to fd3
write 1 GB to fd4
write 1 GB to fd5
write 1 GB to fd6
write 1 GB to fd7 # usually here I run into the problem :-(
write 1 GB to fd8
close (fd1);
close (fd2);
close (fd3);
close (fd4);
close (fd5);
close (fd6);
close (fd7);
close (fd8);
Achim_______________________________________________
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