[CentOS] mismatch_cnt after 5.3 -> 5.4 upgrade

[Ron Loftin]

On Sun, 2009-10-25 at 12:33 -0600, Devin Reade wrote:
> Saturday I did an upgrade from 5.3 (original install) to 5.4.  Saturday
> night, /etc/cron.weekly reported the following:
> 
>        /etc/cron.weekly/99-raid-check:
> 
>        WARNING: mismatch_cnt is not 0 on /dev/md0
> 
I had this happen on a box that I upgraded Friday.  I went ahead and
tested each partition in the affected mirror with badblocks ( found no
errors ) and after multiple resyncs, there was no change.  After similar
experiences with Google, I did run across a note saying that this went
away after a reboot.  I broke down and applied the Micro$lop solution
( reboot ) and the error has gone away.

Like you, I'm interested in a better understanding of this issue, so if
anyone else has more info, I'm all ears. ;>

> md0 holds /boot and resides, mirrored, on sda1 and sdb1. md1 holds
> an LVM volume containing the remaining filesytems, including swap.
> 
> The underlying hardware is just a few months hold, has passed the
> usual memtest stuff, and has been running 5.3 well for a few months.
> 
> I'm *guessing* that due to the timing, this is related to the upgrade.
> I have to admit that I forgot myself and instead of doing the glibc
> updates as recommended, I only did:
> 
> 	yum clean all
> 	yum update yum		  
> 	rpm -e --nodeps perl-5.8.8-18.el5_3.1.i386
> 		(see today's perl thread)
> 	yum update perl.x86_64
> 	yum update
> 	shutdown -r now
> 
> I've taken a backup of /boot dump after the upgrade, but have not yet
> reenabled normal backups.
> 
> My hunch is that something in the upgrade process touched sda1 but not
> sdb1, and that removing sdb1 from the mirror and reattaching it for 
> resync would be sufficient, however I was looking for comments on this
> from anyone with experience or opinion on the matter.  Googling the
> issue doesn't seem to turn up any recent related results.
> 
> Also, could the upgrade have touched the bootblock on sda1 but not 
> sdb1 and thus trigger this problem?
> 
> Devin
-- 
Ron Loftin                      reloftin at twcny.rr.com

"God, root, what is difference ?"       Piter from UserFriendly