During a parity check (this is still running), I got the following entries in in my syslog

 

Please not the the drive that shows up as ata5 below is the cache drive, it is connected to a JMicrom based  add-in controller that has 2 s ata and 1 pata interface.  The cache drive is an older drive and is connected via PATA and seems to not negotiate the correct speed with the controller, it initially comes up as udma/133 and will error and get negotiated down to udma/66 and work fine after that.  All of the other drives are connected to the onboard ich10 controller.  The drive showing the errors (sde) is the parity drive.

 

What do you guys think?

 

I certainly could be wrong, but I am almost positive that ata5 is associated with sde, your parity drive.  These are media errors, with the error flag UNC, so they *appear* to be bad sectors on the parity drive.  However, the drive itself is detecting UNCorrectable errors, reporting them in your SMART report within the last few hours, but with an unknown LBA (0x0fffffff), which is odd.  We have seen this before, but I don't recall the significance, or whether we even figured it out.

 

I would start a SMART long test on this drive, after a power off and reboot.

 

The cache drive is an older drive and is connected via PATA and seems to not negotiate the correct speed with the controller, it initially comes up as udma/133 and will error and get negotiated down to udma/66 and work fine after that.

 

I would replace its cable with a good 80-wire flat ribbon cable, the most likely cause of speed issues with PATA connections.  There are older controllers that only supported UDMA/66, but they would not have initially negotiated at UDMA/133.  The cable is probably not good enough.

I concur.  Sounds like a cable problem.  You're not, by chance, using those "premium" round PATA cables?