Troubleshooting correctable errors?

[Jeff Rizzo <riz%tastylime.net@localhost>]

I recently adding a pair of disks (wd2/wd3) as a mirrored zpool to a 
system, and shortly after doing so, discovered one of the DIMMs was bad, 
which was causing some... issues.


After removing the bad DIMM, most of the issues went away, but I was 
still seeing errors like this occasionally:


[   660.618971] ahcisata0 port 5: device present, speed: 3.0Gb/s
[   660.618971] wd3d: channel reset reading fsbn 3858134944 of 
3858134944-3858135071 (wd3 bn 3858134944; cn 3827514 tn 13 sn 13), xfer 
38, retry 0
[   660.618971] wd3d: channel reset reading fsbn 3858135200 of 
3858135200-3858135327 (wd3 bn 3858135200; cn 3827515 tn 1 sn 17), xfer 
200, retry 0
[   660.618971] wd3d: channel reset reading fsbn 3858135328 of 
3858135328-3858135455 (wd3 bn 3858135328; cn 3827515 tn 3 sn 19), xfer 
298, retry 0
[   661.128968] wd3: soft error (corrected) xfer 38
[   661.128968] wd3: soft error (corrected) xfer 200
[   661.128968] wd3: soft error (corrected) xfer 298


Fine, looks like a dying disk - this didn't make too much sense to me 
(as the disk was pretty new), but spinning rust doesn't last forever.  
After putting it off for a few weeks (during which `zpool status` never 
revealed any problems, even after a scrub), I finally just replaced the 
disk.  Sure enough, the errors are still there. (the ones above are from 
the new disk, actually)


It looks to me like maybe there's a problem on the SATA controller?  I'm 
hoping someone can give me some suggestions of ways to troubleshoot this 
- preferably without a fresh outlay of cash. :)   I have two more free 
ports on the SATA controller, which I will probably try using after 
sending this email, but I'm wondering what else might be going on.  
Suggestions of other stuff to look at gratefully accepted - as far as I 
can tell, it's only this disk (three others seem OK), and all the errors 
have been corrected.

It's a NetBSD 10.1/amd64 system with a XEN3_DOM0 kernel, and a Xen 4.20 
hypervisor, if that matters.

+j