[CentOS] SATA Raid 5 and losing a drive

Tue Apr 11 17:36:47 UTC 2006
Andy Green <andy at warmcat.com>

Hi Folks -

Using CentOS on a server destined to have a dozen SATA drives in it. 
The server is fine, raid 5 is set up on groups of 4 SATA drives.

Today we decide to disconnect one SATA drive to simulate a failure.  The 
box trucked on fine... a little too fine.  We waited some minutes but no 
problem was visible in /proc/mdstat or in /var/log/messages or on the 
console.

I ran mdadm --monitor /dev/md0 and no problem was shown.

We rebooted still without the drive and finally mdadm --monitor reported 
that the array was running in a degraded state.

We reconnected the SATA drive and still nothing was reported and nothing 
happened with the raid state according to /proc/mdstat.

I expected the box to keep on trucking but to become freaked out with 
warnings all over the shop.  What should I have expected in this case 
and what should I do to become aware of evil events like the drive 
melting remotely?

-Andy
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