Re: Newbie with a software RAID question

["Rutledge, Lincoln" <lrutledge@lnlattorneys.com>]

Hi sir,

I set up my first root RAID machine a few months ago, it probably took 10+ hours :(

The man pages tell you everything (raidctl raidframe raid), but there is a lot of info there to weed through.  I read this:

http://www.abstrakt.ch/unix/MINI-HOWTO-openbsd-raid.html

And this was helpful:

http://marc.theaimsgroup.com/?l=openbsd-misc&m=102839903925282&w=2

I printed it out to get me going.  It takes some clever work to set up, you cannot be in a hurry.  I was at first, then I realized that being in a hurry was not helping...

A couple of gotchas to avoid:  

installboot has to be run in single user mode or with a special sysctl setting (I used single user mode, I think you just do a boot -s at the boot: prompt)

You need three kernels.  The default /bsd, a /bsd.raid.auto, and a /bsd.raid.  Because when you screw up, and you are trying to boot from your raid partitions (if you want raid root filesystems), you won't be able to boot to your raid partitions, but the kernel compiled with automatic root raid configuration will try anyway and fail.  So you need a kernel with raid capability, but with no automatic root raid mounting option.  That way you can boot to your non-raid partition and still have access to your raid volumes (like building a ship in a bottle.)

Search the mailing list archives for misc and tech, there are lots of posts about this because it is difficult.

Once you have it working it is sweet though.  I have it on two 3GB IDE drives on our Web server, and once I set up some simple daily scripts to handle backing up data, I feel pretty secure with my data on there.

Also, be aware that in case of a power or disk failure, depending on your hardware and the size of the volumes, it can take some time to rebuid the array.  There is a trick to move the rebuild to the end of the boot cycle (say, after httpd is started) so that your server is back online before rebuilding the array rather than after.  I haven't screwed with this though since mine only seems to take <10 minutes, which is perfectly acceptable downtime in the event that the power is off long enough to drain the UPS.  This was posted recently on misc@.

You can do it...  

Lincoln Rutledge
System Administrator
Luper, Neidenthal, and Logan
lnlattorneys.com