failed drive?

Hi all, I'm having some issues. I'm a little confused, so I was checking our servers today and saw something strange. cat /proc/mdstat shows that 1 device md0 is inactive. I'm not really sure why. I did a bit more digging and testing using smartctl and it says that the device /dev/sdg (part of md0) is failing, estimated to fail within 24 hrs. but if i do df -h it doesn't even show md0, and was talking to a friend and we disagreed. I believe that based on what smrtctl says the drive is failing but not failed yet. he doesn't think its a problem with the drive. do you have any thoughts on this? and why would the device (md0) suddenly be inactive but still show 2 working devices (sdg, sdh)? *(proc/mdstat)* [root@csdatastandby3 bin]# cat /proc/mdstat Personalities : [raid1] [raid10] md125 : active raid10 sdf1[5] sdc1[2] sde1[4] sda1[0] sdb1[1] sdd1[3] 11720655360 blocks super 1.2 512K chunks 2 near-copies [6/6] [UUUUUU] md126 : active raid1 sdg[1] sdh[0] 463992832 blocks super external:/md0/0 [2/2] [UU] md0 : inactive sdh[1](S) sdg[0](S) 6306 blocks super external:imsm unused devices: <none> [root@csdatastandby3 bin]# *(smartctl)* [root@csdatastandby3 bin]# smartctl -H /dev/sdg smartctl 5.43 2012-06-30 r3573 [x86_64-linux-2.6.32-431.17.1.el6.x86_64] (local build) Copyright (C) 2002-12 by Bruce Allen, http://smartmontools.sourceforge.net === START OF READ SMART DATA SECTION === SMART overall-health self-assessment test result: FAILED! Drive failure expected in less than 24 hours. SAVE ALL DATA. Failed Attributes: ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE 5 Reallocated_Sector_Ct 0x0033 002 002 036 Pre-fail Always FAILING_NOW 32288 [root@csdatastandby3 bin]# *(df -h)* [root@csdatastandby3 bin]# df -h Filesystem Size Used Avail Use% Mounted on /dev/md126p4 404G 4.3G 379G 2% / tmpfs 16G 172K 16G 1% /dev/shm /dev/md126p2 936M 74M 815M 9% /boot /dev/md126p1 350M 272K 350M 1% /boot/efi /dev/md125 11T 4.2T 6.1T 41% /data [root@csdatastandby3 bin]# *(mdadm -D /dev/md0* [root@csdatastandby3 bin]# mdadm -D /dev/md0 /dev/md0: Version : imsm Raid Level : container Total Devices : 2 Working Devices : 2 UUID : 32c1fbb7:4479296b:53c02d9b:666a08f6 Member Arrays : /dev/md/Volume0 Number Major Minor RaidDevice 0 8 96 - /dev/sdg 1 8 112 - /dev/sdh [root@csdatastandby3 bin]# thanks -dustink