[CentOS] HA Storage Cookbook?

Les Mikesell lesmikesell at gmail.com
Fri Nov 7 19:03:28 UTC 2008

Gordon McLellan wrote:
> Les,
> That's pretty much my problem.  I was hoping to kill two birds with
> one stone here.  First order of business is to replace the single
> drive with a raid array.  Second order was to replace a single iscsi
> server with duo of machines.  If one machine had some sort of
> non-recoverable problem, the other could pick-up the torch and carry
> on, even if that means I need to "flip a switch" to make it happen.

My solution for semi-critical stuff (i.e. a few minutes of downtime 
won't cost the 6 figures it would take to prevent it) has been to use 
RAID1 in a chassis with hot-swap carriers and keep a spare chassis 
handy.  That way the common case of a disk failure doesn't even cause a 
slowdown and you can rebuild at an off-peak time without shutting down 
and in the much less likely case of a motherboard failure you yank the 
drives, put them in the other box and reboot.  But, that means you are 
probably limited to 6 disks total with half used as mirrors and you 
still need backups for software or site disasters.

The next step up from this would be DRBD to keep hot copies on the spare 
machine but I've always gotten away with one spare chassis for several 
active servers (and sometime using it for testing other things too...).

You do need to know about the NIC hardware address in 
/etc/sysconfig/ifcfg-eth? when swapping disks around, though.

   Les Mikesell
    lesmikesell at gmail.com

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