ioWait brown out

I have a program which is trying to write several dozen
0.25 to 8 MByte files/sec, when recording diagnostics.

My machine gets into a high ioWait situation, and "browns-out".
The machine barely runs for several minutes.

The test code can complete, and the high ioWait continues
for several minutes.

After the program is done, I can do "sudo sync",
which will take several minutes to complete,
then the machine is OK.

I have repeated this on several machines, same results.
I haven even tried writing to NFS... the client machine
browns-out, the server is fine.

I am not talking about some amazingly massive amount of data here.
If things worked, I would be recording about 1G in about 2 sec.
I realize that I should only be able to expect (at worst)
about 50MBytes/sec to disk, hence my 2-second run (no diagnostic
file writes) should take about 20 sec with the diagnostic data dump.
However, this run takes more like 10 minutes, and my machine
goes wanky.

Any idea what might do this?

In general, I am new'ing a 1-2 MB buffer, filling it with
data (2D arrays of floats), then writing it to a file,
then delete[] 'ing the buffer ...
as fast as I can, for some 300 files or so.

Is it not reasonable for me to be able to
create these mid-sized files with a bandwidth
of around (at least) 50MBytes/sec to SATA-II, running ext4?

            aaron
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