[kwlug-disc] Hardware raid vs linux

[Bob Jonkman]

john at netdirect.ca wrote, On 08/20/2009 8:31 PM:
>> The downside in choosing Linux over the cheap RAID card is that if 
>> the primary disk fails the system may fail to boot from the secondary 
>> disk? The BIOS on a cheap RAID card should do that work, but with 
>> Linux there isn't a reliable option.

Yup yup yup.  Some years ago I worked in a department which had just 
purchased shiny new IBM servers.  The server hardware was capable of 
performing RAID, so they had purchased an extra drive for mirroring 
(RAID 1?)  The system ran their document management database, what today 
would be called a CVS.

Eventually, one of the drives died.  It turned out to be the  main 
drive, which, unbeknownst to us, had a hidden partition for booting.  
Also, it turned out that RAID wasn't hardware RAID, but some kind of 
software RAID that only mirrored the visible partition.  Needless to 
say, the server refused to boot from the mirrored drive without the 
hidden partition.  Fortunately, the firmware had an option to restore 
the hidden partition on the second drive, but unfortunately, that nuked 
the partition that contained the only remaining copy of the document 
management database.  I spent a very happy weekend with a nice gentleman 
from IBM, whom I forced to stick around after he had replaced the bad 
drive while I restored the database from tape.

The system was restored with the same configuration, and fortunately 
didn't fail again while I was there.  IBM discontinued that server model 
shortly afterwards...

--Bob.