This is why distributed scale out iSCSI SANs are awesome - particularly the HP StoreVirtual SAN (formerly HP Lefthand P4000).
If you're using the HP P4000 SAN in a best practices configuration, you have redundant switches and redundant nodes. Using HP's Network RAID 10 to provide synchronous replication services across nodes, you essentially have two SANs that are operating as a single SAN, providing both redundancy as well as performance increases. You can also take half of a mirrored pair offline for planned maintenance like firmware & software upgrades, allowing for SAN upgrades without any downtime at all. It eliminates all single points of failure. If you're using iSCSI SAN but not using HP StoreVirtual... you should take a serious look at it.
To a lesser extent, you can do some of this with other SANs (at least basic network path redundancy) - assuming the SAN has more than one network port, they should be connected to different switches (i.e. you should always have at least 2 SAN switches in best practices). This way, if one switch goes offline, planned or unplanned, your servers always have an alternate route to the SAN.
Redundant management modules just protects from one aspect of failure (regardless of whether downtime is planned or unplanned) - there should always be redundant switches so this simply isn't an issue.