Hello, Yes, to all your questions.  Select the PS3900 and either right mouse or in the center action menu, select "Delete Member"    Wait until that completes and then delete the other member.   This will safely remove the member from the group and reset it back to factory defaults.  FYI:  An alternative to manually moving the volumes when you have mulitple pools, is to merge the pools.  Then you can move the old members out one at a time.  This will leave data in that pool.   Then delete the member from group.   
Here is my situation. I have a single group consisting of 5 member spanned out between 3 different storage pools. See below.   ps3900xv è Storage Pool #1 ps3900xv è Storage Pool #1 ps4000e è Storage Pool #2 ps4100e è Storage Pool #2 ps6100xv è Storage Pool #3   Dell / EqualLogic recently EOL’ed the ps3900xv’s so I want to remove them from the group. I have already moved all the data from Storage Pool #1 which consisted of the ps3900xv’s to Storage Pool #3 which is the ps6100xv. In other words, there is no data / volumes on the ps3900xv's anymore. The ps3900xv’s are running firmware version 5.2.5 and the rest of the members are running version 6.0.5. I want to pull the ps3900xv’s to bring it out of a mixed group configuration. My question is can I safely remove those members from the group without any impact to the group or the other members and can this be done during production hours. I am thinking yes but just want to make sure. Thanks! Scott
Removing Members from a Group