AHCI timeout when using ZFS + AIO + NCQ

[Vladislav Prodan]

> >> Essentially the combination of SATA 3 speeds the midplane / backplane
> >> degraded the connection between the MB and HDD enough to cause
> >> the disks to randomly drop when under load.
> >> 
> >> If we connected the disks directly to the MB with SATA cables the
> >> problem went away. In the end we had midplanes changed from an
> >> AHCI pass-through to active LSI controller.
> >> 
> >> So if you have any sort of midplane / backplane connecting your disks
> >> try connecting them direct to the MB / controller via known SATA 3.x
> >> compliant cables and see if that stops the drops.
> >> 
> >> Another test you can do is to force the disks to connect at SATA 2.x
> >> this also fixed it in our case, but wasn't something we wanted to
> >> put into production hence the controller swap.
> >> 
> >> To force SATA 2 speeds you can use the following in /boot/loader.conf
> >> where 'X' is disk identifier e.g. for ada0 X = 0:-
> >> hint.ahcich.X.sata_rev=2
> 
> This is still worth trying as it could still indicate a problem
> with your controller, cables or disks.
> 

Or, simply disable the ahci kernel module and use only ata?


-- 
Vladislav V. Prodan            
System & Network Administrator 
http://support.od.ua           
+380 67 4584408, +380 99 4060508
VVP88-RIPE