diff --git a/mon/lp-optimizer.js b/mon/lp-optimizer.js
index 98ea1f69c..2cb653ea6 100644
--- a/mon/lp-optimizer.js
+++ b/mon/lp-optimizer.js
@@ -50,7 +50,7 @@ async function lp_solve(text)
     return { score, vars };
 }
 
-async function optimize_initial({ osd_tree, pg_count, pg_size = 3, pg_minsize = 2, max_combinations = 10000, parity_space = 1, round_robin = false })
+async function optimize_initial({ osd_tree, pg_count, pg_size = 3, pg_minsize = 2, max_combinations = 10000, parity_space = 1, ordered = false })
 {
     if (!pg_count || !osd_tree)
     {
@@ -92,7 +92,7 @@ async function optimize_initial({ osd_tree, pg_count, pg_size = 3, pg_minsize =
         console.log(lp);
         throw new Error('Problem is infeasible or unbounded - is it a bug?');
     }
-    const int_pgs = make_int_pgs(lp_result.vars, pg_count, round_robin);
+    const int_pgs = make_int_pgs(lp_result.vars, pg_count, ordered);
     const eff = pg_list_space_efficiency(int_pgs, all_weights, pg_minsize, parity_space);
     const res = {
         score: lp_result.score,
@@ -382,11 +382,35 @@ async function optimize_change({ prev_pgs: prev_int_pgs, osd_tree, pg_size = 3,
         {
             differs++;
         }
-        for (let j = 0; j < pg_size; j++)
+    }
+    if (ordered)
+    {
+        for (let i = 0; i < pg_count; i++)
         {
-            if (new_pgs[i][j] != prev_int_pgs[i][j])
+            for (let j = 0; j < pg_size; j++)
             {
-                osd_differs++;
+                if (new_pgs[i][j] != prev_int_pgs[i][j])
+                {
+                    osd_differs++;
+                }
+            }
+        }
+    }
+    else
+    {
+        for (let i = 0; i < pg_count; i++)
+        {
+            const old_map = prev_int_pgs[i].reduce((a, c) => { a[c] = (a[c]|0) + 1; return a; }, {});
+            for (let j = 0; j < pg_size; j++)
+            {
+                if ((0|old_map[new_pgs[i][j]]) > 0)
+                {
+                    old_map[new_pgs[i][j]]--;
+                }
+                else
+                {
+                    osd_differs++;
+                }
             }
         }
     }
diff --git a/mon/mon.js b/mon/mon.js
index a1ef25868..3e198ad24 100644
--- a/mon/mon.js
+++ b/mon/mon.js
@@ -1098,7 +1098,7 @@ class Mon
                     pg_size: pool_cfg.pg_size,
                     pg_minsize: pool_cfg.pg_minsize,
                     max_combinations: pool_cfg.max_osd_combinations,
-                    round_robin: pool_cfg.scheme != 'replicated',
+                    ordered: pool_cfg.scheme != 'replicated',
                 };
                 let optimize_result;
                 if (old_pg_count > 0)
@@ -1121,10 +1121,6 @@ class Mon
                         {
                             pg.push(0);
                         }
-                        while (pg.length > pool_cfg.pg_size)
-                        {
-                            pg.pop();
-                        }
                     }
                     if (!this.state.config.pgs.hash)
                     {
diff --git a/mon/test-optimize-16_2.js b/mon/test-optimize-16_2.js
deleted file mode 100644
index 86987d74b..000000000
--- a/mon/test-optimize-16_2.js
+++ /dev/null
@@ -1,27 +0,0 @@
-// Copyright (c) Vitaliy Filippov, 2019+
-// License: VNPL-1.1 (see README.md for details)
-
-const LPOptimizer = require('./lp-optimizer.js');
-
-const osd_tree = {
-    100: { 1: 1 },
-    200: { 2: 1 },
-    300: { 3: 1 },
-};
-
-async function run()
-{
-    let res;
-    console.log('16 PGs, size=3');
-    res = await LPOptimizer.optimize_initial({ osd_tree, pg_size: 3, pg_count: 16 });
-    LPOptimizer.print_change_stats(res, false);
-    console.log('\nChanging size to 2');
-    res = await LPOptimizer.optimize_change({ prev_pgs: res.int_pgs, osd_tree, pg_size: 2 });
-    LPOptimizer.print_change_stats(res, false);
-    if (res.space < 3*14/16)
-    {
-        throw new Error('Redistribution failed');
-    }
-}
-
-run().catch(console.error);
diff --git a/mon/test-optimize-simple.js b/mon/test-optimize-simple.js
index 97daa6580..70f89047b 100644
--- a/mon/test-optimize-simple.js
+++ b/mon/test-optimize-simple.js
@@ -5,21 +5,45 @@ const LPOptimizer = require('./lp-optimizer.js');
 
 async function run()
 {
-    const osd_tree = { a: { 1: 1 }, b: { 2: 1 }, c: { 3: 1 } };
+    const osd_tree = {
+        100: { 1: 1 },
+        200: { 2: 1 },
+        300: { 3: 1 },
+    };
+
     let res;
 
     console.log('16 PGs, size=3');
-    res = await LPOptimizer.optimize_initial({ osd_tree, pg_size: 3, pg_count: 16 });
+    res = await LPOptimizer.optimize_initial({ osd_tree, pg_size: 3, pg_count: 16, ordered: false });
     LPOptimizer.print_change_stats(res, false);
-
-    console.log('\nReduce PG size to 2');
-    res = await LPOptimizer.optimize_change({ prev_pgs: res.int_pgs.map(pg => pg.slice(0, 2)), osd_tree, pg_size: 2 });
+    assert(res.space == 3, 'Initial distribution');
+    console.log('\nChange size to 2');
+    res = await LPOptimizer.optimize_change({ prev_pgs: res.int_pgs, osd_tree, pg_size: 2, ordered: false });
     LPOptimizer.print_change_stats(res, false);
-
+    assert(res.space >= 3*14/16 && res.osd_differs == 0, 'Redistribution');
     console.log('\nRemove OSD 3');
-    delete osd_tree['c'];
-    res = await LPOptimizer.optimize_change({ prev_pgs: res.int_pgs, osd_tree, pg_size: 2 });
+    const no3_tree = { ...osd_tree };
+    delete no3_tree['300'];
+    res = await LPOptimizer.optimize_change({ prev_pgs: res.int_pgs, osd_tree: no3_tree, pg_size: 2, ordered: false });
     LPOptimizer.print_change_stats(res, false);
+    assert(res.space == 2, 'Redistribution after OSD removal');
+
+    console.log('\n16 PGs, size=3, ordered');
+    res = await LPOptimizer.optimize_initial({ osd_tree, pg_size: 3, pg_count: 16, ordered: true });
+    LPOptimizer.print_change_stats(res, false);
+    assert(res.space == 3, 'Initial distribution');
+    console.log('\nChange size to 2, ordered');
+    res = await LPOptimizer.optimize_change({ prev_pgs: res.int_pgs, osd_tree, pg_size: 2, ordered: true });
+    LPOptimizer.print_change_stats(res, false);
+    assert(res.space >= 3*14/16 && res.osd_differs < 8, 'Redistribution');
+}
+
+function assert(cond, txt)
+{
+    if (!cond)
+    {
+        throw new Error((txt||'test')+' failed');
+    }
 }
 
 run().catch(console.error);
diff --git a/mon/test-optimize-undersized.js b/mon/test-optimize-undersized.js
index 306a5e3da..d1a766e6a 100644
--- a/mon/test-optimize-undersized.js
+++ b/mon/test-optimize-undersized.js
@@ -45,30 +45,45 @@ async function run()
     console.log('Empty tree:');
     let res = await LPOptimizer.optimize_initial({ osd_tree: cur_tree, pg_size: 3, pg_count: 256 });
     LPOptimizer.print_change_stats(res, false);
+    assert(res.space == 0);
     console.log('\nAdding 1st failure domain:');
     cur_tree['dom1'] = osd_tree['dom1'];
     res = await LPOptimizer.optimize_change({ prev_pgs: res.int_pgs, osd_tree: cur_tree, pg_size: 3 });
     LPOptimizer.print_change_stats(res, false);
+    assert(res.space == 12 && res.total_space == 12);
     console.log('\nAdding 2nd failure domain:');
     cur_tree['dom2'] = osd_tree['dom2'];
     res = await LPOptimizer.optimize_change({ prev_pgs: res.int_pgs, osd_tree: cur_tree, pg_size: 3 });
     LPOptimizer.print_change_stats(res, false);
+    assert(res.space == 24 && res.total_space == 24);
     console.log('\nAdding 3rd failure domain:');
     cur_tree['dom3'] = osd_tree['dom3'];
     res = await LPOptimizer.optimize_change({ prev_pgs: res.int_pgs, osd_tree: cur_tree, pg_size: 3 });
     LPOptimizer.print_change_stats(res, false);
+    assert(res.space == 36 && res.total_space == 36);
     console.log('\nRemoving 3rd failure domain:');
     delete cur_tree['dom3'];
     res = await LPOptimizer.optimize_change({ prev_pgs: res.int_pgs, osd_tree: cur_tree, pg_size: 3 });
     LPOptimizer.print_change_stats(res, false);
+    assert(res.space == 24 && res.total_space == 24);
     console.log('\nRemoving 2nd failure domain:');
     delete cur_tree['dom2'];
     res = await LPOptimizer.optimize_change({ prev_pgs: res.int_pgs, osd_tree: cur_tree, pg_size: 3 });
     LPOptimizer.print_change_stats(res, false);
+    assert(res.space == 12 && res.total_space == 12);
     console.log('\nRemoving 1st failure domain:');
     delete cur_tree['dom1'];
     res = await LPOptimizer.optimize_change({ prev_pgs: res.int_pgs, osd_tree: cur_tree, pg_size: 3 });
     LPOptimizer.print_change_stats(res, false);
+    assert(res.space == 0);
+}
+
+function assert(cond, txt)
+{
+    if (!cond)
+    {
+        throw new Error((txt||'test')+' failed');
+    }
 }
 
 run().catch(console.error);