Anthony,

You should update to v5.0.8, then to v5.2.2 (v5.0.8 is the latest interim version for the v5.0.x family of FW)

You would then update each member in the group to v5.0.8 first.  This is done to each member “one at a time” (ex. update member1, restart member1, then go on to the next member, repeating update/restart process for each member until all members are at the same version of the firmware).

Once the group is at v5.0.8 (i.e., all the members), you can then repeat the process for the upgrade to v5.2.2 (update member1, restart the member, then go on to the next member, repeating this update/restart process for each member).

(Optional) If the Hosts systems are high availability, you may want to consider doing a “rolling update” as discussed in the KB article on the support site (search the KB for “ARRAY: Updating a multi-member group without down-time”).  This operation will require you to have sufficient free space in your pool to permit you to remove all volume data from one member at a time. The system requires that 10% free space in an affected pool remain afterwards before it will allow you to remove an array from that pool. If you do not have sufficient free space, you will not be permitted to move your arrays out of your existing pools.

If the rolling update is not an option for you, you need to ensure that all your initiators are configured properly to ensure they can “ride out” the firmware update restart (typically 15-30 seconds).  Again on the support site on the FW download page is a document titled: “iSCSI Initiator and Operating System Considerations”

The release notes for each version also has some additional information.

There isn’t any undo command for a firmware update, typically if a situation causes the firmware to not update, you should open a support case so that they can work with you to correct the situation.

-joe