diff --git a/lp/mon.js b/lp/mon.js
index 2b2a708c..0972003d 100644
--- a/lp/mon.js
+++ b/lp/mon.js
@@ -443,6 +443,7 @@ class Mon
         levels.host = levels.host || 100;
         levels.osd = levels.osd || 101;
         const tree = { '': { children: [] } };
+        let up_osds = {};
         for (const node_id in this.state.config.node_placement||{})
         {
             const node_cfg = this.state.config.node_placement[node_id];
@@ -465,6 +466,11 @@ class Mon
                 let reweight = this.state.config.osd[osd_num] && Number(this.state.config.osd[osd_num].reweight);
                 if (reweight < 0 || isNaN(reweight))
                     reweight = 1;
+                if (this.state.osd.state[osd_num] && reweight > 0)
+                {
+                    // React to down OSDs immediately
+                    up_osds[osd_num] = true;
+                }
                 tree[osd_num] = tree[osd_num] || { id: osd_num, parent: stat.host };
                 tree[osd_num].level = 'osd';
                 tree[osd_num].size = reweight * stat.size / 1024 / 1024 / 1024 / 1024; // terabytes
@@ -487,7 +493,7 @@ class Mon
             tree[parent].children.push(tree[node_id]);
             delete node_cfg.parent;
         }
-        return LPOptimizer.flatten_tree(tree[''].children, levels, this.config.failure_domain, 'osd');
+        return { up_osds, osd_tree: LPOptimizer.flatten_tree(tree[''].children, levels, this.config.failure_domain, 'osd') };
     }
 
     async stop_all_pgs(pool_id)
@@ -562,6 +568,8 @@ class Mon
         });
         for (let i = 0; i < new_pgs.length || i < prev_pgs.length; i++)
         {
+            // FIXME: etcd has max_txn_ops limit, and it's 128 by default
+            // Sooo we probably want to change our storage scheme for PG histories...
             request.compare.push({
                 key: b64(this.etcd_prefix+'/pg/history/'+pool_id+'/'+(i+1)),
                 target: 'MOD',
@@ -649,8 +657,9 @@ class Mon
         // Take configuration and state, check it against the stored configuration hash
         // Recalculate PGs and save them to etcd if the configuration is changed
         // FIXME: Also do not change anything if the distribution is good enough and no PGs are degraded
+        const { up_osds, osd_tree } = this.get_osd_tree();
         const tree_cfg = {
-            osd_tree: this.get_osd_tree(),
+            osd_tree,
             pools: this.state.config.pools,
         };
         const tree_hash = sha1hex(stableStringify(tree_cfg));
@@ -706,32 +715,102 @@ class Mon
                 if (old_pg_count != optimize_result.int_pgs.length)
                 {
                     console.log(
-                        `PG count for pool ${pool_id} (${pool_cfg.name || 'unnamed'}) `+
-                        `changed from: ${old_pg_count} to ${optimize_result.int_pgs.length}`
+                        `PG count for pool ${pool_id} (${pool_cfg.name || 'unnamed'})`+
+                        ` changed from: ${old_pg_count} to ${optimize_result.int_pgs.length}`
                     );
                 }
                 LPOptimizer.print_change_stats(optimize_result);
                 this.save_new_pgs_txn(etcd_request, pool_id, prev_pgs, optimize_result.int_pgs, pg_history);
             }
             this.state.config.pgs.hash = tree_hash;
-            etcd_request.compare.push(
-                { key: b64(this.etcd_prefix+'/mon/master'), target: 'LEASE', lease: ''+this.etcd_lease_id },
-                { key: b64(this.etcd_prefix+'/config/pgs'), target: 'MOD', mod_revision: ''+this.etcd_watch_revision, result: 'LESS' },
-            );
-            etcd_request.success.push(
-                { requestPut: { key: b64(this.etcd_prefix+'/config/pgs'), value: b64(JSON.stringify(this.state.config.pgs)) } },
-            );
-            const res = await this.etcd_call('/kv/txn', etcd_request, this.config.etcd_mon_timeout, 0);
-            if (!res.succeeded)
+            await this.save_pg_config();
+        }
+        else
+        {
+            // Nothing changed, but we still want to check for down OSDs
+            let changed = false;
+            for (const pool_id in this.state.config.pools)
             {
-                console.log('Someone changed PG configuration while we also tried to change it. Retrying in '+this.config.mon_change_timeout+' ms');
-                this.schedule_recheck();
-                return;
+                const pool_cfg = this.state.config.pools[pool_id];
+                if (!this.validate_pool_cfg(pool_id, pool_cfg, false))
+                {
+                    continue;
+                }
+                for (const pg_num in ((this.state.config.pgs.items||{})[pool_id]||{})||{})
+                {
+                    const pg_cfg = this.state.config.pgs.items[pool_id][pg];
+                    if (!Number(pg_cfg.primary) || !up_osds[pg_cfg.primary])
+                    {
+                        const alive_set = pg_cfg.osd_set.filter(osd_num => up_osds[osd_num]);
+                        const new_primary = alive_set.length ? alive_set[Math.floor(Math.random()*alive_set.length)] : 0;
+                        if (pg_cfg.primary != new_primary)
+                        {
+                            console.log(
+                                `Moving pool ${pool_id} (${pool_cfg.name || 'unnamed'}) PG ${pg_num}`+
+                                ` primary OSD from ${pg_cfg.primary} to ${new_primary}`
+                            );
+                            changed = true;
+                            pg_cfg.primary = new_primary;
+                        }
+                    }
+                }
+            }
+            if (changed)
+            {
+                await this.save_pg_config();
             }
-            console.log('PG configuration successfully changed');
         }
     }
 
+    async save_pg_config(etcd_request = { compare: [], success: [] })
+    {
+        etcd_request.compare.push(
+            { key: b64(this.etcd_prefix+'/mon/master'), target: 'LEASE', lease: ''+this.etcd_lease_id },
+            { key: b64(this.etcd_prefix+'/config/pgs'), target: 'MOD', mod_revision: ''+this.etcd_watch_revision, result: 'LESS' },
+        );
+        etcd_request.success.push(
+            { requestPut: { key: b64(this.etcd_prefix+'/config/pgs'), value: b64(JSON.stringify(this.state.config.pgs)) } },
+        );
+        const res = await this.etcd_call('/kv/txn', etcd_request, this.config.etcd_mon_timeout, 0);
+        if (!res.succeeded)
+        {
+            console.log('Someone changed PG configuration while we also tried to change it. Retrying in '+this.config.mon_change_timeout+' ms');
+            this.schedule_recheck();
+            return;
+        }
+        console.log('PG configuration successfully changed');
+    }
+
+    // Schedule next recheck at least at <unixtime>
+    schedule_next_recheck_at(unixtime)
+    {
+        this.next_recheck_at = !this.next_recheck_at || this.next_recheck_at > unixtime
+            ? unixtime : this.next_recheck_at;
+        const now = Date.now()/1000;
+        if (this.next_recheck_timer)
+        {
+            clearTimeout(this.next_recheck_timer);
+            this.next_recheck_timer = null;
+        }
+        if (this.next_recheck_at < now)
+        {
+            this.next_recheck_at = 0;
+            this.schedule_recheck();
+        }
+        else
+        {
+            this.next_recheck_timer = setTimeout(() =>
+            {
+                this.next_recheck_timer = null;
+                this.next_recheck_at = 0;
+                this.schedule_recheck();
+            }, now-this.next_recheck_at);
+        }
+    }
+
+    // Schedule a recheck to run after a small timeout (1s)
+    // If already scheduled, cancel previous timer and schedule it again
+    // This is required for multiple change events to trigger at most 1 recheck in 1s
     schedule_recheck()
     {
         if (this.recheck_timer)
@@ -917,15 +996,30 @@ class Mon
             this.state.config.global = this.state.config.global || {};
             this.config = this.state.config.global;
             this.check_config();
+            for (const osd_num in this.state.osd.stats)
+            {
+                // Recheck PGs <osd_out_time> later
+                this.schedule_next_recheck_at(
+                    !this.state.osd.stats[osd_num] ? 0 : this.state.osd.stats[osd_num].time+this.config.osd_out_time
+                );
+            }
         }
         else if (key.join('/') === 'config/pools')
         {
             for (const pool_id in this.state.config.pools)
             {
+                // Adjust pool configuration so PG distribution hash doesn't change on recheck()
                 const pool_cfg = this.state.config.pools[pool_id];
                 this.validate_pool_cfg(pool_id, pool_cfg, true);
             }
         }
+        else if (key[0] === 'osd' && key[1] === 'stats')
+        {
+            // Recheck PGs <osd_out_time> later
+            this.schedule_next_recheck_at(
+                !this.state.osd.stats[key[2]] ? 0 : this.state.osd.stats[key[2]].time+this.config.osd_out_time
+            );
+        }
     }
 
     async etcd_call(path, body, timeout, retries)