Hello, i want to ask how i can discover whether some of the HDDs in HW Raid 1 is dead?
Following are related messages (which do not solve issue for me)

# cat /proc/mdstat
Personalities :
unused devices: <none>
# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg-root 904G
# smartctl --scan
/dev/sda -d scsi # /dev/sda, SCSI device
# smartctl -a /dev/sda -d scsi
smartctl 5.43 2012-06-30 r3573
Copyright (C) 2002-12 by Bruce Allen, http://smartmontools.sourceforge.net


Vendor: Dell
Product: VIRTUAL DISK
Revision: 1028
User Capacity: 999,647,346,688 bytes [999 GB]
Logical block size: 512 bytes
Logical Unit id: 0x600508e0000000004ef585164852be01
Device type: disk
Local Time is: Thu Dec 18 14:52:59 2014 UTC
Device does not support SMART


Error Counter logging not supported
Device does not support Self Test logging
Im having Centos 5.11 64bit, i tried:
"yum install lshw"
and then run "lshw" it shown all hardware info including name of raid controller. When googled that name, i found i can install "mpt-status" tool (Googled: mpt-status centos 5 PS: another alternative is: lsiutil) so i installed in my case by "yum install daemonize -y; rpm -ivh http://sven.stormbind.net/mpt-status-rhel/mpt-status-1.2.0-3.el5.centos.x86_64.rpm" then needed to run "modprobe mptctl". then see hardware raid status by command "mpt-status" or "mpt-status -i 0" returned:
ioc0 vol_id 0 type IM, 2 phy, 930 GB, state OPTIMAL, flags ENABLED
ioc0 phy 1 scsi_id 9 ATA MM1000EBKAF HPG0, 931 GB, state ONLINE, flags NONE
ioc0 phy 0 scsi_id 1 ATA MM1000EBKAF HPG0, 931 GB, state ONLINE, flags NONE
but i assume i canot tell whether drive is failed according this output? or im wrong?

Update: i think this command can tell failure.

mpt-status -n shows even Raid level:
ioc:0 vol_id:0 type:IM raidlevel:RAID-1 num_disks:2 size(GB):931 state: OPTIMAL flags: ENABLED
ioc:0 phys_id:1 scsi_id:8 vendor:SEAGATE product_id:ST31000424SS revision:0006 size(GB):931 state: ONLINE flags: NONE sync_state: 100 ASC/ASCQ:0xff/0xff SMART ASC/ASCQ:0xff/0xff
ioc:0 phys_id:0 scsi_id:1 vendor:SEAGATE product_id:ST31000424SS revision:0006 size(GB):931 state: ONLINE flags: NONE sync_state: 100 ASC/ASCQ:0xff/0xff SMART ASC/ASCQ:0xff/0xff
scsi_id:1 100%
scsi_id:0 100%
mpt-status for rhel 5,6,7 backup (src):
mpt-status-rhel.zip