[nSLUG] Hardware versus software RAID

Dop Ganger nslug at fop.ns.ca
Mon Nov 1 14:01:03 AST 2004


On Mon, 1 Nov 2004, Steven R. Baker wrote:

> I've talked to some folks that have had limited success with IDE
> compiled as a module doing a hotswap of disks.  When you remove/insert
> the module, the controllers are scanned.  Apparently there's work taking
> place in the kernel to make this safer, but I'm not sure how safe it
> will be given that the BIOS isn't detecting the drives at module insert
> time.

Very dodgy. I've managed to blow IDE ports before now on ATX boards by
unplugging the IDE cable without checking the power was unplugged (it's
the sort of thing that you only do once). My preferred strategy for
replacing a blown drive in a server is:

1. Unplug all network connections, allowing the failover server to take
over the service.
2. Shutdown the machine gracefully, replace the hardware, make sure it all
works.
3. Bring the machine up all the way then plug in the network cables,
allowing heartbeat to bring services back up.

If you're working on a setup that's using a LocalDirector or LVS or
similar, you can just remove the server and wait for it to finish serving
current connections for completely zero downtime.

Cheers... Dop.

!DSPAM:418679e3192191462382368!




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