I just installed SL5.3 on a Supermicro PDSBE motherboard and its disk i/o is painfully slow; about 3MB/s.  The system has SATA drives but the kernel sees them as /dev/hdx devices.  There is also a ata_piix message at the beginning of bootup that says "no available legacy port".  I'm guessing the failure to recognize the SATA drives as /dev/sdx and the slow disk i/o are related to this cryptic message.

I ran a Fedora 11 live CD on the system and it can do disk i/o easily 20-30 times faster which is closer to what I expect.  100MB/s or more.  I'm pretty sure the problem is kernel related.

I tried switching the SATA mode in the BIOS to compability instead of enhanced.  It didn't make any difference.  I wasn't expecting any.  The compatibility vs native stuff, I thought, was something that was done when SATA support for spotty.  The SATA controller is an Intel ICH8 which I figure should be well supported.

I also looked at the dumps of hdparm both under SL53 and Fedora 11.  The features enabled are the same for both.  There are additional features listed under Fedora 11, all SCT (SMART Command Transport) related.  There is also a whole bunch of dma modes displayed in both hdparm -t dumps.  On SL53 there is a * next to udma5 while it's next to udma6 under Fedora.  I'm not sure what this means.

Any ideas on how to proceed?  Build a custom kernel?  Which I am reluctant to do since I rely on SL for updates.

Ken