[ILUG] Extremely slow/CPU intensive SATA IO on 2 CPU HT server.

[David Golden]

On Sunday 12 March 2006 19:02, David Wilson wrote:

> The only thing I can think of is having the hosting company pull up
> the BIOS and turn off hyperthreading, something I've been meaning to
> do for various other reasons anyway.
>
>     Linux 2.6.15.1 #1 SMP Fri Jan 20 19:47:58 GMT 2006 i686
>     scsi0 : ata_piix
>     ATA: abnormal status 0x7F on port 0xC407
>     ata1: SATA max UDMA/133 cmd 0xC800 ctl 0xC482 bmdma 0xC000 irq 17
>     SCSI device sda: 586072368 512-byte hdwr sectors (300069 MB)
>
> Does anyone have any pointers? Thanks,
>

Not even sure this is the problem:

There is an evil "combined mode" "feature" of the some piix hardware 
that causes the ata_piix to decide it can't in good conscience do 
proper DMA safely without some advice from the sysadmin:  it seems the 
PIIX/ICH* chipsets sometimes make attached devices appear as BOTH IDE 
and ATA devices, at the same time, or something like that! Fiddling 
with BIOS options and perhaps trying the kernel option 
"combined_mode=libata" might help (some sources say 
"ata_piix.combined_mode=libata", which in turn suggests to me there 
might be a "options ata_piix combined_mode=libata" for modular kernels 
(untested, nor have I looked at the source to verify...).   Anyway, 
should be enough to be going on with for a google search...) .

BEWARE. Fiddling with this stuff can lead to spectacular data loss 
incidents if you're not careful, obviously enough.