How to check that a low replication speed is caused by the source machine

Diagnosing low replication speed caused by the source machine

Challenge

The Acura Control Panel shows that one of the machines is being replicated with an undesirably low speed.

Cause

There are several factors that may interfere with a replication and cause a "bottleneck" issue for its speed. But before focusing on the network bandwidth capacity or potentially faulty settings, please consider that the disk being processed may be solely responsible for a low reading speed due to a poor IOPS performance on the source machine.

In order to gather the relevant statistics and provide their interactive visualization, every Acura instance is provisioned with a Grafana web application. Its interface is available at port 30082 (http:// <Acura's IP:30082>/). Please contact our Support team to get the access credentials. 

Once logged into Grafana, select the " Stats per device" dashboard by clicking on the " Home" drop-down menu in the top left corner and then on the  Default folder.



The Machine ID is available in the Acura UI. Сlick on the green circle with the letter "i" to the left of the machine's name in the Machines Groups section. Then copy the Machine ID to Grafana into the device_id field.




Idea
The graphs can be generated according to customer, device or snapshot. A desired time frame can be selected in the top right corner.



The highlighted stats (see the picture above) provide a quick hint towards the source disk performance.
The " agent_stats.Disk Read Speed" value shows how fast the agent is reading from the disk. Its max level can indicate the current replication speed limit..
The " agent_stats.Agent Disk Reading Time" value shows the time needed by the agent to read a block within a single request. The numbers can then be compared to those of healthy machines in order to detect a corresponding low point of disk performance.
Once the issue has been identified, the customer's decision to proceed may vary depending on the migration/DR strategy, which will require further adjustments should time be a pressing concern.

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