[K12OSN] Server mixing up sda/sdb/sdc, etc. at boot time.

Carl Keil carl at snarlnet.com
Thu Feb 19 23:04:13 UTC 2009

Hey folks,

I've got a weird problem.  Googling has provided me with links to other 
people experiencing the same thing (so I'm not crazy, maybe), but no 

I'm getting smartd messages that I have a failing hard drive in my RAID 
array.  So I thought I'd be proactive and swap out the drive since I 
have a spare.  I have 4 sata heads on the mobo.  I have sda as the 
unraided boot drive and sdb + sdc configured as md0 for the /home 
directory.  I figured that sata1 would be sda, sata2 would be sdb, etc.  
So I pulled the drive that was on sata3 because the message said that 
sdc had the problem.  When I rebooted, the server wouldn't boot up?   
Turns out that sata3 is sda?!  I've tried pulling each of the drives in 
turn and it seems like the computer reshuffles the drives almost 
randomly.  So they all take turns being sda/sdb, etc., depending on 
which are plugged, unplugged.  Sometimes the raid shows up, sometimes it 
can't be found.  With only one drive pulled, out of 4 drives, only 3 of 
which are supposed to be in use.

Is there a way to lock these down so that they always correspond to 
sda/sdb, etc?  It seems like that would have to happen in BIOS, but it 
doesn't look like an option.  If the drives aren't assigned 
sequentially, how am I supposed to swap out the drive?

Any help would be appreciated.


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