RAID Munging Question

[Matthew J. Brodeur]

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On Fri, 5 Apr 2002, Kent Borg wrote:

> I recently got a new box up and running Red Hat 7.2.  What's more, I
> put in two 60 GB disks in software RAID 1 so that if one dies the
> other should keep running (even swapping because swap has its own RAID
> 1 partition).  Either disk should be bootable, too.  How fun!

   Note that the system will probably NOT keep running if one drive fails.  
My experience has been that when an IDE drive goes down the system becomes 
very unhappy, but this may be different with newer hardware/kernels.  The 
good news is that (again, from experience) the data on the "good" drive 
was intact and usable after rebooting with the dead drive removed.


> My /home partition is RAID 0 (no redundancy, but bigger and faster)
> instead of RAID 1 (redundancy, smaller, somewhat faster read than raw
> disk). 

   Not to start an argument, but isn't RAID 1 actually slower than single 
disk access?  It would seem that writing to two drives would take longer 
than writing one, especially with IDE.


>   3. Edit /etc/raidtab so /dev/md5 line that currently reads
>      "raid-level 0" will read "raid-level 1",
> 
>   4. "# unmount /home"

   I'd swap these two, just for sanity.  It shouldn't matter one bit if 
you change raidtab while the FS is mounted, but it seems like a bad idea.  
You should also verify that the other raid options, such as 
"chunk-size", make sense.


> Do you people think it will work?  Will it work?

   The only thing I didn't see was unpacking the tarball of the original 
/home.  You probably would have noticed that on your own, though. ;)
   Other than that I think it'll work.  It looks like you've got all the 
steps for adding a new RAID volume, which is essentially what you'll be 
doing.  


- -- 
     -Matt

Silver's law: If Murphy's law can go wrong it will. 


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