Re: [patch] multipath RAID personality, 2.4.10-pre9

["Ragnar Kjørstad" <kernel@ragnark.vestdata.no>]

On Tue, Sep 18, 2001 at 08:39:46PM +0100, Adrian Bridgett wrote:
> Do you have plans to change this?  I know that the SDD software for AIX load
> balances between paths (and I think EMC's Powerpaths do for AIX too), DMP
> (from Veritas) for Solaris doesn't.
> 
> In fact that brings up another point - which path do you use by default?  If
> you have the SAN situation where you have a farm of servers each with two FC
> cards two two FC switches and then to two ports on a storage array, you
> don't want everything going to the first switch.  Just picking one path to
> use at random would be preferable (unless you want to swap every other
> servers cables around).

I think the multipath driver would benefit from something like the
different modes in the new network bonding driver:
* round robin
* active backup policy
* XOR

(Not sure if XOR would be needed for md?)

I think some other ideas can be stolen from the bonding driver as well,
as the problem is very simular - e.g. the concept of low level drivers
(optionally) delivering status information, so md don't have to try and
fail to detect a link is down, and the timeout settings.


-- 
Ragnar Kjørstad
Big Storage