[CentOS] SATA Raid 5 and losing a drive

Tue Apr 11 17:42:47 UTC 2006
Joshua Baker-LePain <jlb17 at duke.edu>

On Tue, 11 Apr 2006 at 6:36pm, Andy Green wrote

> 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.

Did you try doing any I/O to the array?  In my limited experience with 
software RAID, it won't notice a drive missing until it tries to do 
something with said drive.

To really test it, I'd disconnect the drive while you have something 
disk intensive running.  I like 
<http://people.redhat.com/dledford/memtest.html>, which unpacks and then 
diffs multiple copies of the Linux source tree.  It'll have the system 
stressed *and* let you know if there any problems with the array running 
in degraded mode.

Joshua Baker-LePain
Department of Biomedical Engineering
Duke University