When the VRA’s CPU and memory are overloaded, the IO buffers can fill up and cause delays on the replication, and therefore, bitmap sync can occur.


Identify the affected VRA

  1. Open the ZVM UI.
  2. Open the VPGs tab.
  3. Select the relevant VPG.
  4. Click on the “Protected VMs” tab.
  5. Expand the ‘Protection Host’ and ‘Recovery Host’ tabs.

Review the VRA Performance within the Zerto UI

In the ZVM GUI, click on ‘Setup’ and on the VRA you’d like to monitor.
  •  The Local memory refers to the local buffer – the buffer that is involved when the VRA acts as a production VRA, collecting and sending I/Os to the peer VRA.
  • The Remote memory graph refers to the buffer that is involved when the VRA acts as a recovery VRA.
If we the graphs breach above 70%, the VRA resources should be increased or balance the load across more VRAs. Please note that The VRA can utilize up to 16 GB of RAM and 2 vCPUs.

Review the VRA resources within vCenter 

We can review the performance graphs within vCenter for more information. To review the performance graphs, please follow the steps below:
  1. Connect to the vCenter UI (Both Flash and HTML 5 are fine).
  2. Click on the relevant VRA -> Monitor -> Performance -> Advanced.
  3. Click on ‘Chart Options’.
  4. We will review three different charts Datastore, CPU and Memory.

Storage delay 

This check should be performed on the recovery (cloud) site.
Under the 'Chart Options', select Datastore and make sure to check both Read Latency and Write Latency and click OK.


By default, Zerto will start throttling I/Os if either one of the latency values goes above 40 ms. This was designed to protect the actual storage devices from overheating. This value is tweakable, but Zerto strongly recommends approaching this matter from the storage perspective to ensure the longevity of your storage devices.
If you’d like to tweak the bad I/O throttling value, please contact AssureStor support.


Memory Consumption 

Under the 'Chart Options', select 'Memory' and make sure to check Active, Consumed, and Host consumed %.
  1. The ‘Consumed’ graph will show us the consumed memory from the Host (the ‘total’ as far as the VRA is concerned).
  2. The Active graph will show us how much is being utilized at any given point in time.
  3. The ‘Host consumed %’ will translate the ‘Active’ graph to a percentage out of the ‘Consumed’ value. 
In case the Memory usage is above 70% Zerto recommends trying to balance the load across more VRAs or add more RAM to the VRA.


CPU Consumption 

Under the 'Chart Options', select 'CPU' and choose Usage %.
If the usage is above 70% Zerto recommends trying to balance the load across more VRAs or add more CPU to the VRA.