Update change-metrics-storage.md (#14640)

1 files changed, 12 insertions, 1 deletions

diff --git a/docs/store/change-metrics-storage.md b/docs/store/change-metrics-storage.md
index 7f9681884b..f3a7c97fcc 100644
--- a/docs/store/change-metrics-storage.md
+++ b/docs/store/change-metrics-storage.md
@@ -38,11 +38,22 @@ on the maximum retention and the memory used by Netdata is described in detail,
     
     # Tier 1, per minute data
     dbengine tier 1 multihost disk space MB = 128
-
+    dbengine tier 1 update every iterations = 60
+    
     # Tier 2, per hour data
     dbengine tier 2 multihost disk space MB = 64
+    dbengine tier 2 update every iterations = 60
 ```
 
+The default "update every iterations" of 60 means that if a metric is collected per second in Tier 0, then
+we will have a data point every minute in tier 1 and every minute in tier 2. 
+
+You may add, or remove tiers and/or modify these multipliers, as long as the product of all the "update every" does not exceed 65535. 
+
+e.g. If you simply add a fourth tier by setting `storage tiers` to 4 and defining the disk space for it, 
+the product of the update every will be 60 * 60 * 60 = 216,000, which is > 65535. So you'd need to reduce  
+the `update every iterations` of the tiers, to stay under the limit.
+
 The exact retention that can be achieved by each tier depends on the number of metrics collected. The more 
 the metrics, the smaller the retention that will fit in a given size. The general rule is that Netdata needs 
 about **1 byte per data point on disk for tier 0**, and **4 bytes per data point on disk for tier 1 and above**.