libata error/reset

["Dan Noé" <dpn@isomerica.net>]

Just after midnight last night, during an rsync job which copies a lot 
of data onto my backup disk (half of a Linux software RAID 1), I 
received the following:

-- SNIP --
ata3.00: exception Emask 0x10 SAct 0x0 SErr 0x10000 action 0xe frozen
ata3.00: irq_stat 0x00400000, PHY RDY changed
ata3: SError: { PHYRdyChg }
ata3.00: cmd 35/00:10:3f:00:34/00:00:22:00:00/e0 tag 0 dma 8192 out
          res 50/00:00:4e:01:18/00:00:22:00:00/e0 Emask 0x10 (ATA bus error)
ata3.00: status: { DRDY }
ata3: hard resetting link
ata3: link is slow to respond, please be patient (ready=0)
ata3: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
ata3.00: qc timeout (cmd 0xec)
ata3.00: failed to IDENTIFY (I/O error, err_mask=0x5)
ata3.00: revalidation failed (errno=-5)
ata3: failed to recover some devices, retrying in 5 secs
ata3: hard resetting link
ata3: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
ata3.00: configured for UDMA/100
ata3: EH complete
sd 2:0:0:0: [sdc] 625142448 512-byte hardware sectors (320073 MB)
sd 2:0:0:0: [sdc] Write Protect is off
sd 2:0:0:0: [sdc] Mode Sense: 00 3a 00 00
sd 2:0:0:0: [sdc] Write cache: enabled, read cache: enabled, doesn't 
support DPO or FUA
-- SNIP --

The system seems to be working fine now, and there was not even a RAID 
failure reported by the md system.  Is this something I should be 
concerned about? Hardware issue, software bug?

Linux colobus 2.6.26.3 #1 SMP Thu Aug 21 10:15:38 EDT 2008 i686 Intel(R) 
Pentium(R) 4 CPU 3.20GHz GenuineIntel GNU/Linux

00:1f.2 SATA controller: Intel Corporation 82801FR/FRW (ICH6R/ICH6RW) 
SATA Controller (rev 03)

I am using the libata ahci driver.  There are four drives crammed into a 
1U with hotplug trays, but AFAIK no one was poking around the system.

Thanks much,
Dan

-- 
Dan Noé
Software Engineer
Lime Brokerage LLC
781-370-2518