Patrol read errors on Dell Perc 6...

[Scott Mitchell]

Hi all,

I have a Dell R710 server running 8.0R/amd64, with a PERC 6 RAID controller 
and four SAS drives in a RAID10 configuration.  The RAID controller does a 
weekly "patrol read" that threw up a load of errors in the most recent run:

+========================================================================
+seqNum: 0x00000b5e
+Time: Tue Aug  3 22:06:15 2010
+
+Code: 0x00000071
+Class: 0
+Locale: 0x02
+Event Description: Unexpected sense: PD 02(e0x20/s2) Path 5000c5000561dfc9, 
CDB: 2f 00 19 21 40 00 00 10 00 00, Sense: 3/11/00
+Event Data:
+       Device ID: 2
+       Enclosure Index: 32
+       Slot Number: 2
+       CDB Length: 10
+       CDB Data:
+       002f 0000 0019 0021 0040 0000 0000 0010 0000 0000 0000 0000 0000 0000 
0000 0000 Sense Length: 18
+       Sense Data:
+       00f0 0000 0003 0019 0021 004b 00e1 000a 0000 0000 0000 0000 0011 0000 
0081 0080 0000 0097 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 
0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 
0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 
0000 0000 0000 0000 0000
+
+========================================================================
+seqNum: 0x00000b5f
+Time: Tue Aug  3 22:06:15 2010
+
+Code: 0x0000005d
+Class: 0
+Locale: 0x02
+Event Description: Patrol Read corrected medium error on PD 02(e0x20/s2) at 
19214be1
+Event Data:
+       Device ID: 2
+       Enclosure Index: 32
+       Slot Number: 2
+       LBA: 421612513
+
+========================================================================

...and a lot more of the same.  Everything else on the machine is still 
working fine as far as I can tell, and the status of the RAID volume is still 
reported as "Optimal":

Checking status of MFI RAID controllers:
Adapter: 0
------------------------------------------------------------------------
Physical Drive Information:
ENC SLO DEV SEQ MEC OEC PFC LPF STATE
32  0   0   2   0   0   0   0   Online
32  1   1   2   0   0   0   0   Online
32  2   2   2   234 0   0   0   Online
32  3   3   2   0   0   0   0   Online

Virtual Drive Information:
VD  DRV RLP RLS RLQ STS    SIZE        STATE         NAME
0   2   1   3   0   64kB   1143552MB   Optimal       SVN

BBU Information:
TYPE  TEMP  OK   RSOC  ASOC      RC   CC  ME
BBU    20C  Yes   92%   77% 1377mAh    7  2%

I'm not sure how I should interpret these errors and what action, if any, I 
should take.  Do I need to replace - or at least rebuild - the offending 
drive?  Can I do that safely without taking the machine down?  The box is 
covered by Dell support but I'd like to get all my facts straight before I 
call them and they try to pin a hardware problem on this "FreeBSD" thing 
they've never heard of before...

Many thanks,

	Scott