On Sat, 14 Jul 2007, jeff stern wrote:

hi, everyone..  i have a problem.

SUMMARY

i've got a linux software RAID1 setup, with 2 SATA drives (/dev/sdf1,
/dev/sdg1) set up to be /dev/md0. these 2 drives together hold my
/home directories. the / and / partitions are on another drive, a
standard parallel IDE (/dev/hda). (I can provide more hardware
information if someone needs it).

the problem is that new errors (mismatch_cnt discrepancies) between
the two disks keep coming up. weekly. even daily, and i dont know what
to do, or how to handle it.

How many mismatch_cnts between two almost-new drives running in a
healthy RAID1 array should one expect in a year? in a month? a day?

And more importantly, What do i do now?

EXTENDED DESCRIPTION OF PROBLEM

i first noticed this problem when i downloaded the fedora core 7 .iso,
and did a checksum on it, and it didn't match. with a little more
investigating, i found that i could make a copy of any large file on
disk, and its copy would sometimes match, sometimes not.

here is a typical session:
------------------------------------------------------------------------------------------
$ cp F-7-i386-DVD.iso F.iso
$ cmp F-7-i386-DVD.iso F.iso
F-7-i386-DVD.iso F.iso differ: byte 1033827385, line 3789612
$ cmp F-7-i386-DVD.iso F.iso
$ cmp F-7-i386-DVD.iso F.iso
F-7-i386-DVD.iso F.iso differ: byte 1033827385, line 3789612
$ cmp F-7-i386-DVD.iso F.iso
F-7-i386-DVD.iso F.iso differ: byte 8870221, line 37265
$ cmp F-7-i386-DVD.iso F.iso
F-7-i386-DVD.iso F.iso differ: byte 8870221, line 37265
$ _
------------------------------------------------------------------------------------------

Something sounds very strange here, I have a script that runs the 'check' 
once a week for my RAID1 partitions and it is generally 0 every time, 
except for the swap parition (occasionally)- which Neil has mentioned-- is 
normal.  You bringup a lot of good points though; however, I am not sure 
why you are experiencing so many mismatches.....

Justin.