On 12/30/2010 05:41 PM, James wrote:
Inline.
On Thu, Dec 30, 2010 at 05:13, Giovanni Tessore<giotex@xxxxxxxxxx> wrote:
On 12/30/2010 04:20 AM, James wrote:
Can someone point me in the right direction?
(a) what causes these errors precisely?
(b) is the error benign? How can I determine if it is *likely* a
hardware problem? (I imagine it's probably impossible to tell if it's
HW until it's too late)
(c) are these errors expected in a RAID array that is heavily used?
(d) what kind of errors should I see regarding "read errors" that
*would* indicate an imminent hardware failure?
(a) these errors usually come from defective disk sectors. raid recostructs
the missing sector from parity from other disks in the array, then rewrites
the sector on the defective disk; if the sector is rewritten without error
(maybe the hd remaps the sector into its reserved area), then just the log
messages is displayed.
(b) with raid-6 it's almost benign; to get troubles you should get a read
error on same sector for>2 disks; or have 2 disks failed and out of the
array and get a read error on one of the other disks while recostructing the
array; or have 1 disk failed and get a read error on same sector on>1 disk
while recostructing (with raid-5 it's almost dangerous instead, as you can
have big troubles if a disk fails and you get a read error on another disk
while recostructing; that happened to me!)
(c) no; it's also a good rule to perform a periodic scrub of the array
(check of the array), to reveal and correct defective sectors
(d) check smart status of the disks, for "relocated sectors count"; also if
md superblock is>= 1 there is a persistent count of corrected read errors
for each device into /sys/block/mdXX/md/dev-XX/errors, when this counter
reaches 256 the disk is marked failed; ihmo when a disk is giving even few
corrected read errors in a short interval its better to replace it.
Good call.
Here's the output of the reallocated sector count:
~ # for i in a b c d ; do smartctl -a /dev/sd$i | grep Realloc ; done
5 Reallocated_Sector_Ct 0x0033 100 100 036 Pre-fail
Always - 1
5 Reallocated_Sector_Ct 0x0033 100 100 036 Pre-fail
Always - 3
5 Reallocated_Sector_Ct 0x0033 100 100 036 Pre-fail
Always - 5
5 Reallocated_Sector_Ct 0x0033 100 100 036 Pre-fail
Always - 1
Are these values high? Low? Acceptable?
How about values like "Raw_Read_Error_Rate" and "Seek_Error_Rate" -- I
believe I've read those are values that are normally very high...is
this true?
~ # for i in a b c d ; do smartctl -a /dev/sd$i | grep
Raw_Read_Error_Rate ; done
1 Raw_Read_Error_Rate 0x000f 116 099 006 Pre-fail
Always - 106523474
1 Raw_Read_Error_Rate 0x000f 114 099 006 Pre-fail
Always - 77952706
1 Raw_Read_Error_Rate 0x000f 117 099 006 Pre-fail
Always - 137525325
1 Raw_Read_Error_Rate 0x000f 118 099 006 Pre-fail
Always - 179042738
...and...
~ # for i in a b c d ; do smartctl -a /dev/sd$i | grep
Seek_Error_Rate ; done
7 Seek_Error_Rate 0x000f 072 060 030 Pre-fail
Always - 14923821
7 Seek_Error_Rate 0x000f 072 060 030 Pre-fail
Always - 15648709
7 Seek_Error_Rate 0x000f 072 060 030 Pre-fail
Always - 15733727
7 Seek_Error_Rate 0x000f 071 060 030 Pre-fail
Always - 14279452
Thoughts appreciated.
As I know, Reallocated_Sector_Ct is the most meaningful SMART parameter
related to disk sectors health.
Also check for Current_Pending_Sector (sector that gave read on error
and has not been reallocated yet).
The values of your disks seems quite safe at the moment.
Be proactive if the value grows in short time.
I had same problem this week, one of my disk gave >800 reallocated read
errors.
The disk was still marked good and alive into array, but I replaced it
immediately.
Regards.
--
Cordiali saluti.
Yours faithfully.
Giovanni Tessore
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
