Re: ata timeouts under load

Kris Kennaway wrote:
> I am getting timeouts on 8.0b4/HEAD when I do a lot of ZFS I/O to a pool
> on ad4:
> 
> atapci0: <VIA 6420 SATA150 controller> port
> 0xc800-0xc807,0xc400-0xc403,0xc000-0xc007,0xb800-0xb803,0xb400-0xb40f,0xb000-0xb0ff
> irq 20 at device 15.0 on pci0
> ata2: <ATA channel 0> on atapci0
> ata3: <ATA channel 1> on atapci0
> ata0: <ATA channel 0> on atapci1
> ata1: <ATA channel 1> on atapci1
> 
> ad4: 476940MB <WDC WD5000AAKS-00TMA0 12.01C01> at ata2-master SATA150
> ad4: WARNING - SETFEATURES SET TRANSFER MODE taskqueue timeout -
> completing request directly
> ad4: WARNING - SETFEATURES SET TRANSFER MODE taskqueue timeout -
> completing request directly
> ad4: WARNING - SETFEATURES ENABLE RCACHE taskqueue timeout - completing
> request directly
> ad4: WARNING - SETFEATURES ENABLE WCACHE taskqueue timeout - completing
> request directly
> ad4: WARNING - SET_MULTI taskqueue timeout - completing request directly
> ad4: TIMEOUT - WRITE_DMA48 retrying (1 retry left) LBA=344052040
> ad4: WARNING - SETFEATURES SET TRANSFER MODE taskqueue timeout -
> completing request directly
> ad4: WARNING - SETFEATURES SET TRANSFER MODE taskqueue timeout -
> completing request directly
> 
> It becomes stuck in a loop displaying the above and is unable to
> complete further I/O operations.  I wonder if it is just batching up a
> lot of I/O and then timing out because it is busy, and then not
> recovering from this state?
> 
> Any ideas what could be wrong?

There are two different kinds of timeouts we can see:
 - first one, "ad4: WARNING - ..." is just a queue waiting timeout. It
is not the reason, but consequence of the problem. And I have doubts
that it is reasonable to do it.
 - second one, "TIMEOUT - WRITE_DMA48 ..." is a real command execution
timeout. I don't know whether this is result of some improper error
recovery, or you drive indeed lost required servo information near
LBA=344052040 and tries to find it too long. You can try to read that
sector and nearby ones with dd.

-- 
Alexander Motin