Pg stuck stale...why?

[Mark Kirkwood <mark.kirkwood@catalyst.net.nz>]

I am seeing this:

# ceph -s
    health HEALTH_WARN 256 pgs stale; 256 pgs stuck stale
    monmap e1: 3 mons at 
{ved1=192.168.122.11:6789/0,ved2=192.168.122.12:6789/0,ved3=192.168.122.13:6789/0}, 
election epoch 18, quorum 0,1,2 ved1,ved2,ved3
    osdmap e62: 4 osds: 4 up, 4 in
     pgmap v47148: 768 pgs: 512 active+clean, 256 stale+active+clean; 
2224 MB data, 15442 MB used, 86907 MB / 102350 MB avail
    mdsmap e1: 0/0/1

In particular 256 pgs stuck stale - I've tried a) waiting a while 
(overnight),  b) a rolling restart of all 4 osd's,  c) restarting all 
ceph services on all 4 nodes. All without changing this.

As far as I understand what stuck state means, I can't see why they need 
to stay that way, given all osd's and mon's are up. (I have no mds 
configured)....any ideas? Or is this just expected?

Regards

Mark