diff --git a/.gitignore b/.gitignore
index 90669e9..86d15af 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,5 +10,6 @@ test.sh
 nimrod.properties
 /.lein-failures
 /target/
-/nimrod-data/
-/nimrod.conf
\ No newline at end of file
+/nimrod-data*
+/nimrod.conf
+/.tmp.zipeg.1333558157188866000/
diff --git a/nimrod2.conf b/nimrod2.conf
index a3cf5f2..a79248e 100644
--- a/nimrod2.conf
+++ b/nimrod2.conf
@@ -6,6 +6,6 @@ store {
         "defrag.limit" : 3
     }
     sampling {
-        "test" : 10
+        "test.frequency" : 10
     }
 }
diff --git a/src/nimrod/core/stat.clj b/src/nimrod/core/stat.clj
index f0bb3b1..10efcec 100644
--- a/src/nimrod/core/stat.clj
+++ b/src/nimrod/core/stat.clj
@@ -11,16 +11,16 @@
     (util/unrationalize (/ (+ previous-variance (* (- value previous-average) (- value current-average))) (dec samples)))
     0))
 
-(defn median [total index-fn]
+(defn median [total read-fn]
   (if (odd? total)
-    (index-fn (Math/round (/ total 2.0)))
-    (util/unrationalize (/ (+ (index-fn (inc (/ total 2))) (index-fn (/ total 2))) 2))))
+    (read-fn (Math/round (/ total 2.0)))
+    (util/unrationalize (/ (+ (read-fn (inc (/ total 2))) (read-fn (/ total 2))) 2))))
 
-(defn percentiles [total percentages index-fn]
+(defn percentiles [total percentages read-fn]
   (into {} 
     (for [p percentages]
       (cond 
-        (and (> p 0) (< p 100)) (let [rank (Math/round (+ (* (/ p 100) total) 0.5))] [(keyword (str p "th")) (index-fn rank)])
-        (= 0 p) [(keyword (str p "th")) (index-fn 1)]
-        (= 100 p) [(keyword (str p "th")) (index-fn total)]
+        (and (> p 0) (< p 100)) (let [rank (Math/round (+ (* (/ p 100) total) 0.5))] [(keyword (str p "th")) (read-fn rank)])
+        (= 0 p) [(keyword (str p "th")) (read-fn 1)]
+        (= 100 p) [(keyword (str p "th")) (read-fn total)]
         :else (throw (IllegalArgumentException. (str "Out of bounds percentile: " p)))))))
\ No newline at end of file
diff --git a/src/nimrod/core/store.clj b/src/nimrod/core/store.clj
index cc3fe46..12d1ea2 100644
--- a/src/nimrod/core/store.clj
+++ b/src/nimrod/core/store.clj
@@ -18,15 +18,16 @@
 (defonce default-cache-entries 1000)
 (defonce default-cache-results 1000000)
 (defonce default-defrag-limit 0)
-(defonce default-sampling-threshold 1)
+(defonce default-sampling-factor 10)
+(defonce default-sampling-frequency 0)
 
 (defonce default-age oneMinute)
 
 (defn- to-json [v]
   (json/parse-smile v true (fn [_] #{})))
 
-(defn- sample? [old-value new-value threshold]
-  (not (= (int (/ old-value threshold)) (int (/ new-value threshold)))))
+(defn- do-sampling? [samples sampling-frequency]
+  (and (not (zero? sampling-frequency)) (= samples sampling-frequency)))
 
 (defprotocol Store
   (init [this])
@@ -54,9 +55,11 @@
       (sql/with-connection connection-factory
         (sql/transaction 
           (sql/do-prepared 
-            "CREATE CACHED TABLE metrics (ns LONGVARCHAR, type LONGVARCHAR, id LONGVARCHAR, timestamp BIGINT, raw DOUBLE, metric LONGVARBINARY, PRIMARY KEY (ns,type,id))")
+            "CREATE CACHED TABLE metrics (ns LONGVARCHAR, type LONGVARCHAR, id LONGVARCHAR, seq BIGINT, timestamp BIGINT, raw DOUBLE, metric LONGVARBINARY, PRIMARY KEY (ns,type,id))")
           (sql/do-prepared 
-            "CREATE CACHED TABLE history (ns LONGVARCHAR, type LONGVARCHAR, id LONGVARCHAR, timestamp BIGINT, seq BIGINT GENERATED ALWAYS AS IDENTITY, raw DOUBLE, metric LONGVARBINARY, PRIMARY KEY (ns,type,id,timestamp,seq))")))
+            "CREATE CACHED TABLE history (ns LONGVARCHAR, type LONGVARCHAR, id LONGVARCHAR, seq BIGINT, timestamp BIGINT, raw DOUBLE, metric LONGVARBINARY, PRIMARY KEY (ns,type,id,seq))")
+          (sql/do-prepared 
+            "CREATE INDEX history_idx ON history (ns,type,id,timestamp)")))
       (catch Exception ex))
     (sql/with-connection connection-factory
       (sql/transaction 
@@ -69,31 +72,60 @@
           ["SELECT * FROM metrics"] 
           (doseq [metric all-metrics] 
             (dosync 
-              (alter memory assoc-in [(metric :ns) (metric :type) (metric :id) :raw] (metric :raw))
-              (alter memory assoc-in [(metric :ns) (metric :type) (metric :id) :metric] (to-json (metric :metric)))))))))
+              (alter memory assoc-in [(metric :ns) (metric :type) (metric :id) :seq] (metric :seq))
+              (alter memory assoc-in [(metric :ns) (metric :type) (metric :id) :metric] (to-json (metric :metric)))
+              (alter memory assoc-in [(metric :ns) (metric :type) (metric :id) :samples] 0)))))))
   
   (set-metric [this metric-ns metric-type metric-id metric raw]
-    (let [old-raw-value (get-in @memory [metric-ns metric-type metric-id :raw])
+    (let [current-seq-value (or (get-in @memory [metric-ns metric-type metric-id :seq]) 0)
+          current-samples (or (get-in @memory [metric-ns metric-type metric-id :samples]) 0)
+          new-seq-value (inc current-seq-value)
+          new-samples (inc current-samples)
+          new-raw-value raw
           new-json-metric (json/generate-smile metric)
           new-metric-timestamp (metric :timestamp)
-          sampling-threshold (or 
-                               (sampling metric-ns) 
-                               (sampling (str metric-ns "." metric-type))
-                               (sampling (str metric-ns "." metric-type "." metric-id))
-                               default-sampling-threshold)]
+          sampling-factor (or 
+                            (sampling (str metric-ns "." metric-type "." metric-id ".factor"))
+                            (sampling (str metric-ns "." metric-type ".factor"))
+                            (sampling (str metric-ns ".factor")) 
+                            default-sampling-factor)
+          sampling-frequency (or 
+                               (sampling (str metric-ns "." metric-type "." metric-id ".frequency"))
+                               (sampling (str metric-ns "." metric-type ".frequency"))
+                               (sampling (str metric-ns ".frequency"))
+                               default-sampling-frequency)]
+      ; Increment sequence prior to actually using it to avoid duplicated entries:
+      (dosync
+        (alter memory assoc-in [metric-ns metric-type metric-id :seq] new-seq-value))
+      ; Insert metric/history:
       (sql/with-connection connection-factory 
         (sql/transaction 
           (sql/update-or-insert-values 
             "metrics"
             ["ns=? AND type=? AND id=?" metric-ns metric-type metric-id]
-            {"ns" metric-ns "type" metric-type "id" metric-id "timestamp" new-metric-timestamp "raw" raw "metric" new-json-metric})
-          (when (or (nil? old-raw-value) (sample? old-raw-value raw sampling-threshold))
-            (sql/insert-record
-              "history"
-              {"ns" metric-ns "type" metric-type "id" metric-id "timestamp" new-metric-timestamp "raw" raw "metric" new-json-metric}))))
+            {"ns" metric-ns "type" metric-type "id" metric-id "timestamp" new-metric-timestamp "seq" new-seq-value "raw" new-raw-value "metric" new-json-metric})
+          (sql/insert-record
+            "history"
+            {"ns" metric-ns "type" metric-type "id" metric-id "timestamp" new-metric-timestamp "seq" new-seq-value "raw" new-raw-value "metric" new-json-metric})))
       (dosync
-        (alter memory assoc-in [metric-ns metric-type metric-id :raw] raw)
-        (alter memory assoc-in [metric-ns metric-type metric-id :metric] metric))))
+        (alter memory assoc-in [metric-ns metric-type metric-id :metric] metric))
+      ; Optionally sample:
+      (sql/with-connection connection-factory 
+        (sql/transaction     
+          (if (do-sampling? new-samples sampling-frequency)
+            (do 
+              (loop [record new-seq-value samples new-samples to-delete (- new-samples (/ new-samples sampling-factor))]
+                (if ( <= (int (* samples (rand))) to-delete)
+                  (do
+                    (sql/delete-rows "history" 
+                      ["ns=? AND type=? AND id=? AND seq=?"
+                       metric-ns metric-type metric-id record])
+                    (when (> (dec to-delete) 0) (recur (dec record) (dec samples) (dec to-delete))))
+                  (recur (dec record) (dec samples) to-delete)))
+              (dosync
+                (alter memory assoc-in [metric-ns metric-type metric-id :samples] 0)))
+            (dosync
+              (alter memory assoc-in [metric-ns metric-type metric-id :samples] new-samples)))))))
   
   (remove-metric [this metric-ns metric-type metric-id]
     (sql/with-connection connection-factory 
diff --git a/test/nimrod/conf/setup_test.clj b/test/nimrod/conf/setup_test.clj
index cb9115d..f631c09 100644
--- a/test/nimrod/conf/setup_test.clj
+++ b/test/nimrod/conf/setup_test.clj
@@ -19,4 +19,4 @@
         (setup "nimrod2.conf")
         (is (= "nimrod-data/db" @path))
         (is (= {"cache.entries" 1 "cache.results" 2 "defrag.limit" 3} @options))
-        (is (= {"test" 10} @sampling)))))
\ No newline at end of file
+        (is (= {"test.frequency" 10} @sampling)))))
\ No newline at end of file
diff --git a/test/nimrod/core/store_test.clj b/test/nimrod/core/store_test.clj
index 4bf595b..4a133c0 100644
--- a/test/nimrod/core/store_test.clj
+++ b/test/nimrod/core/store_test.clj
@@ -75,33 +75,33 @@
   (let [metric-ns-1 "1" metric-type-1 "gauge" metric-id-1 "test" 
         metric-1-1 {:value 1 :timestamp 1}
         metric-1-2 {:value 2 :timestamp 2}
-        metric-1-3 {:value 10 :timestamp 3}
+        metric-1-3 {:value 3 :timestamp 3}
         metric-ns-2 "2" metric-type-2 "gauge" metric-id-2 "test" 
         metric-2-1 {:value 1 :timestamp 1}
-        metric-2-2 {:value 10 :timestamp 2}
-        metric-2-3 {:value 100 :timestamp 3}
+        metric-2-2 {:value 2 :timestamp 2}
+        metric-2-3 {:value 3 :timestamp 3}
         metric-ns-3 "3" metric-type-3 "gauge" metric-id-3 "test" 
         metric-3-1 {:value 1 :timestamp 1}
-        metric-3-2 {:value 100 :timestamp 2}
-        metric-3-3 {:value 1000 :timestamp 3}]
+        metric-3-2 {:value 2 :timestamp 2}
+        metric-3-3 {:value 3 :timestamp 3}]
     (set-metric store metric-ns-1 metric-type-1 metric-id-1 metric-1-1 1)
     (set-metric store metric-ns-1 metric-type-1 metric-id-1 metric-1-2 2)
-    (set-metric store metric-ns-1 metric-type-1 metric-id-1 metric-1-3 10)
+    (set-metric store metric-ns-1 metric-type-1 metric-id-1 metric-1-3 3)
     (set-metric store metric-ns-2 metric-type-2 metric-id-2 metric-2-1 1)
-    (set-metric store metric-ns-2 metric-type-2 metric-id-2 metric-2-2 10)
-    (set-metric store metric-ns-2 metric-type-2 metric-id-2 metric-2-3 100)
+    (set-metric store metric-ns-2 metric-type-2 metric-id-2 metric-2-2 2)
+    (set-metric store metric-ns-2 metric-type-2 metric-id-2 metric-2-3 3)
     (set-metric store metric-ns-3 metric-type-3 metric-id-3 metric-3-1 1)
-    (set-metric store metric-ns-3 metric-type-3 metric-id-3 metric-3-2 100)
-    (set-metric store metric-ns-3 metric-type-3 metric-id-3 metric-3-3 1000)
+    (set-metric store metric-ns-3 metric-type-3 metric-id-3 metric-3-2 2)
+    (set-metric store metric-ns-3 metric-type-3 metric-id-3 metric-3-3 3)
     (testing "Metric history values with sampling configured on metrics namespace"
       (let [history (read-history store metric-ns-1 metric-type-1 metric-id-1 #{} nil 0 Long/MAX_VALUE)]
-        (is (= [metric-1-3 metric-1-1] (history :values)))))
-      (testing "Metric history values with sampling configured on metrics namespace and type"
+        (is (= 2 (count (history :values))))))
+    (testing "Metric history values with sampling configured on metrics namespace and type"
       (let [history (read-history store metric-ns-2 metric-type-2 metric-id-2 #{} nil 0 Long/MAX_VALUE)]
-        (is (= [metric-2-3 metric-2-1] (history :values)))))
+        (is (= 2 (count (history :values))))))
     (testing "Metric history values with sampling configured on metrics namespace, type and id"
       (let [history (read-history store metric-ns-3 metric-type-3 metric-id-3 #{} nil 0 Long/MAX_VALUE)]
-        (is (= [metric-3-3 metric-3-1] (history :values)))))))
+        (is (= 2 (count (history :values))))))))
 
 (defn set-and-remove-metric-history [store]
   (let [metric-ns "1" metric-type "gauge" metric-id "1" 
@@ -232,7 +232,9 @@
   (set-and-read-metric-history-with-old-values-too (new-disk-store (java.io.File/createTempFile "test" "4")))
   (set-and-read-metric-history-by-age (new-disk-store (java.io.File/createTempFile "test" "5")))
   (set-and-read-metric-history-by-tags (new-disk-store (java.io.File/createTempFile "test" "6")))
-  (set-and-read-metric-history-with-sampling (new-disk-store (java.io.File/createTempFile "test" "7") {} {"1" 10 "2.gauge" 100 "3.gauge.test" 1000}))
+  (set-and-read-metric-history-with-sampling 
+    (new-disk-store (java.io.File/createTempFile "test" "7") {} 
+      {"1.factor" 2 "1.frequency" 2 "2.gauge.factor" 2 "2.gauge.frequency" 2 "3.gauge.test.factor" 2 "3.gauge.test.frequency" 2}))
   (set-and-remove-metric-history (new-disk-store (java.io.File/createTempFile "test" "8")))
   (set-and-remove-metric-history-by-age (new-disk-store (java.io.File/createTempFile "test" "9")))
   (set-and-aggregate-metric-history (new-disk-store (java.io.File/createTempFile "test" "10")))