linux multipath - change device alias safely

Question

I'm running RHEL 5.2 connected to a NetApp over FC. The server is running a database on mpathNN devices that can not be stopped. I need to add a new LUN and give it a specific alias (rather than mpathNN). I know how to set this up in multipath.conf, but I don't know the wwid of the LUN yet. I also know this can be achieved by restarting multipathd, but don't know if this is safe.

Is it safe to restart multipathd without i/o interruption?

or, is there another way I can enable the alias specified in multipath.conf once I've presented it to the host?

thanks!

Solution

Yes, you can safely restart multipathd. It is only responsible for checking for failed paths and listening for new paths. It is not directly involved in i/o. To understand the different parts of the multipath system, read The Linux multipath implementation.

Comments

[c4f4t0r]

add alias in multipath.conf and use "multipathd -k "reconfigure" " that works