READ_DMA, WRITE_DMA errors

[Steve]

I've found tons of emails, news messages, listserv messages, and even 
some bug reports of this seemingly common error.

So, I had been running 5.2 on a server, and, updated to 5.3. Got the 
READ_DMA and WRITE_DMA error and retries. So, figuring it might be a bad 
update, took a new drive. put it in, loaded 5.4 for grins, and, same 
issue, lots of these errors, eventually destroying the FS. Played around 
with various settings, no avail. So, took it back, got different box, 
everything new. Same problem, new install of 5.4

So, took it back, got another with another MB (different model), but, 
same maker (ASUS). Didn't have endless time to spend on production 
machine. Sure enough, same problem. It's an ASUS A7V880. Controller is 
SATA VT8237. Played around with tons of settings, eventually, after 
reading various messages out there, discovered one that resolved the 
problem. Had to set hw.ata.ata_dma="0". Of course, there is the obvious 
downside to that! Speed!

But it stinks to have "decent" hardware, yet, have to cripple the 
machine. The place I got the equipment at runs ASUS only and has 
thousands of them running under other OSes. Wished I had stayed with the 
old FreeBSD version and old hardware now. I have not seen anyone that 
has ever said the problem was being (or had been) solved though. I see 
the bug reports, I take it no one has actually pinpointed the problem 
though. BUT, I do hope it is understood that this is fairly widespread, 
for me, the likelihood of 3 pcs, 2 different MB models, and, *complete* 
new hardware for each of the 3 pcs kind of rules out hardware being 
broken, might be badly designed, but, certainly not defective hardware.

I do hope someone can eventually figure this out, seems to be extremely 
common, and, definitely a problem for a stable release named 5.4.

Steve
www.powersystemsdirect.com