It doesn't seem you can lose data even when you might otherwise expect to ;)
I setup a small replica set using
mongod --fork --logpath a.log --smallfiles --oplogSize 50 --port 27001 --dbpath data/z1 --replSet z
mongod --fork --logpath b.log --smallfiles --oplogSize 50 --port 27002 --dbpath data/z2 --replSet z
mongod --fork --logpath c.log --smallfiles --oplogSize 50 --port 27003 --dbpath data/z3 --replSet z
And initalized it:
> rs.initiate(
{ _id:'z',
members:[
{ _id:1, host:'localhost:27001' },
{ _id:2, host:'localhost:27002' },
{ _id:3, host:'localhost:27003' }
]
}
);
Then I killed all three processes:
kill -9 25542 25496 25483
Next I brought one of them back up
mongod --fork --logpath c.log --smallfiles --oplogSize 50 --port 27003 --dbpath data/z3
and inserted a doc
> db.foo.insert({a:1})
Then I killed that process
kill -9 25885
and brought the replica set back online using
mongod --for