Most members are up and rs.reconfig() command sent to primary, but still seems to require all members be up.

set2:PRIMARY> rs.status()
{
"set" : "set2",
"date" : ISODate("2011-02-05T07:48:59Z"),
"myState" : 1,
"members" : [
{
"_id" : 0,
"name" : "rs2a:27018",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 555,
"optime" :

{ "t" : 1296892137000, "i" : 2 }

,
"optimeDate" : ISODate("2011-02-05T07:48:57Z"),
"lastHeartbeat" : ISODate("2011-02-05T07:48:58Z")
},
{
"_id" : 1,
"name" : "rs2b:27018",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"optime" :

{ "t" : 1296892138000, "i" : 1 }

,
"optimeDate" : ISODate("2011-02-05T07:48:58Z"),
"self" : true
},
{
"_id" : 2,
"name" : "rs2arbiter:27018",
"health" : 1,
"state" : 7,
"stateStr" : "ARBITER",
"uptime" : 171846,
"optime" :

{ "t" : 0, "i" : 0 }

,
"optimeDate" : ISODate("1970-01-01T00:00:00Z"),
"lastHeartbeat" : ISODate("2011-02-05T07:48:58Z")
},
{
"_id" : 3,
"name" : "rs2c:27018",
"health" : 0,
"state" : 6,
"stateStr" : "(not reachable/healthy)",
"uptime" : 0,
"optime" :

{ "t" : 0, "i" : 0 }

,
"optimeDate" : ISODate("1970-01-01T00:00:00Z"),
"lastHeartbeat" : ISODate("1970-01-01T00:00:00Z"),
"errmsg" : "socket exception"
},
{
"_id" : 4,
"name" : "rs2d:27018",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 499342,
"optime" :

{ "t" : 1296884936000, "i" : 2 }

,
"optimeDate" : ISODate("2011-02-05T05:48:56Z"),
"lastHeartbeat" : ISODate("2011-02-05T07:48:57Z")
}
],
"ok" : 1
}
set2:PRIMARY> rs.reconfig(cfg)
{
"assertion" : "need most members up to reconfigure, not ok : rs2c:27018",
"assertionCode" : 13144,
"errmsg" : "db assertion failure",
"ok" : 0
}