Silent RAID-1 degradation on CentOS 5?

["John Abreau-2" <user=184@nabble.blu.org>]

 I have a production server running CentOS 5 that I originally 
set up to use software RAID, and today I noticed that RAID 
wasn't active. 

When I built the system, I partitioned the disks in the graphical 
installer. I  made /dev/sda1 and /dev/sdb1 a 100 GB RAID-1 device 
on /dev/md0, and /dev/sda2 and /dev/sdb2 a 700 GB RAID-1 device 
on /dev/md1. I formatted /dev/md0 as ext3, and made /dev/md1 
an LVM physical volume, then created several logical volumes 
within it. 

Today the machine is using /dev/sda1 instead of /dev/md0, and 
/dev/sdb2 instead of /dev/md1.  The partition types used to be 
"Linux raid autodetect" (fd), but now they're "Linux" (83) and 
"Linux LVM" (8e). 

smartctl shows that both disks are healthy. pvdisplay complains 
about a duplicate PV with the same UUID. 

What could have caused this to silently fail like this, and how 
can I restore RAID safely? 

We had a power outage a few weeks ago that lasted longer than 
the UPS's battery capacity; I suppose that could be the underlying 
cause of it degrading to non-RAID status. But why would it 
do that silently? 


    # mount | grep /boot 
    /dev/sda1 on /boot type ext3 (rw) 

    # pvdisplay 
      Found duplicate PV v81JZ6Kq1oWjD3PaQUORjnabNu4BQzpn: using 
/dev/sdb2 not /dev/sda2 
      --- Physical volume --- 
      PV Name               /dev/sdb2 
      VG Name               EurekaVG 
      PV Size               698.53 GB / not usable 28.56 MB 
      Allocatable           yes 
      PE Size (KByte)       32768 
      Total PE              22352 
      Free PE               11570 
      Allocated PE          10782 
      PV UUID               v81JZ6-Kq1o-WjD3-PaQU-ORjn-abNu-4BQzpn 

    # fdisk -l /dev/sda 
    
    Disk /dev/sda: 750.1 GB, 750156374016 bytes 
    255 heads, 63 sectors/track, 91201 cylinders 
    Units = cylinders of 16065 * 512 = 8225280 bytes 
    
       Device Boot      Start         End      Blocks   Id  System 
    /dev/sda1   *           1          13      104391   83  Linux 
    /dev/sda2              14       91200   732459577+  8e  Linux LVM 

    # fdisk -l /dev/sdb 
    
    Disk /dev/sdb: 750.1 GB, 750156374016 bytes 
    255 heads, 63 sectors/track, 91201 cylinders 
    Units = cylinders of 16065 * 512 = 8225280 bytes 
    
       Device Boot      Start         End      Blocks   Id  System 
    /dev/sdb1   *           1          13      104391   83  Linux 
    /dev/sdb2              14       91200   732459577+  8e  Linux LVM 

    # mdadm --detail /dev/md0 
    mdadm: md device /dev/md0 does not appear to be active. 

    # mdadm --detail /dev/md1 
    mdadm: cannot open /dev/md1: No such file or directory 

    # smartctl -d ata -H /dev/sda 
    smartctl version 5.36 [i686-redhat-linux-gnu] Copyright (C) 2002-6 
Bruce Allen 
    Home page is http://smartmontools.sourceforge.net/
    
    === START OF READ SMART DATA SECTION === 
    SMART overall-health self-assessment test result: PASSED 

    # smartctl -d ata -H /dev/sdb 
    smartctl version 5.36 [i686-redhat-linux-gnu] Copyright (C) 2002-6 
Bruce Allen 
    Home page is http://smartmontools.sourceforge.net/
    
    === START OF READ SMART DATA SECTION === 
    SMART overall-health self-assessment test result: PASSED 


-- 
John Abreau 
IT Manager 
Zuken USA 
238 Littleton Rd., Suite 100 
Westford, MA 01886 
T: 978-392-1777            F: 978-692-4725 
M: 978-764-8934 
E: [hidden email]  W: www.zuken.com 


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