[luau] improving sustainable write to disk rates

[Charles Lockhart]

MonMotha wrote:

> What kind of RAID controller?  If it has an upgradable cache (like my 
> MegaRAID can actually take fast page SIMMs), by all means upgrade it! 
> 64MB of cache can do amazing things for smaller (a few hundred megs) 
> writes :)
>
> Also, you'd be amazed what setting things with hdparm can do (at least 
> for IDE drives).  However, cache is a HUGE factor in sustained write 
> performance.

The system is a Compaq Proliant DL360 server.  The RAID controller is 
embedded, and I don't think the darn thing can be upgraded, though not 
too sure on this point (I should just quit being lazy and open the case 
and look).  Right now it's configured with only 8MB of cache, and looks 
optimized for READ operations (well, they have some setting called the 
"accelerator ratio", and it's 100% dedicated to READ ops), with no 
apparent way of changing that (at least that's what their tools indicate).

I'm really not up to speed on the practical side of RAID.

The controller is Compaq's Smart Array Raid controller, and is located 
on a 32bit pci bus.  The drives are both SCSI, and it looks like the 
stripe size is 128kB.

My test program is writing 4000  4MB files, and I end up with an overall 
data rate of around 40MBps, which is about half of what I'd been hoping 
for.

-Charles