EMC ECS VDC Erasure Coding Test

ECS protects data within a site by mirroring the data onto multiple nodes, and by using erasure coding to break down data chunks into multiple fragments and distribute the fragments across nodes. Erasure coding (EC) reduces the storage overhead and ensures data durability and resilience against disk and node failures. By default, the storage engine implements the Reed-Solomon 12 + 4 erasure coding scheme in which an object is broken into 12 data fragments and 4 coding fragments. The resulting 16 fragments are dispersed across the nodes in the local site. When an object is erasure coded, ECS can read the object directly from the 12 data fragments without any decoding or reconstruction. The code fragments are used only for object reconstruction when a hardware failure occurs. ECS also supports a 10 + 2 scheme for use with cold storage archives to store objects that do not change frequently and do not require the more robust default EC scheme.

The purpose of this test is to monitor the erasure coding process and collect metrics around the same. The insights gained through the metrics help administrators to make sure that process is working fine, and identify issues if any, early in the process.

Target of the test : A Dell EMC Elastic Cloud Storage System

Agent deploying the test : A remote agent

Outputs of the test : One set of results for each Virtual Data Centre (VDC)

Configurable parameters for the test
Parameter	Description
Test period	How often should the test be executed .
Host	The host for which the test is to be configured. Since the storage device is managed using the IP address of its storage controller, the same will be displayed as host.
Port	The port number at which the specified host listens. By default, this is NULL.
ECS REST API Port	This is the port at which REST API connectivity is provided. By default, port 4443 is used.
Username and Password	To collect performance metrics from the target storage device, the eG agent should be configured with the credentials of a user who is vested with "read-only" privileges to access REST API of the target storage device. Specify the credentials of such a user in the Username and Password text boxes.
Confirm Password	Confirm the password by retyping it here.
Timeout Seconds	Specify the time duration for which this test should wait for a response from the storage system in the Timeout text box. By default, this is 60 seconds.

Measurements made by the test
Measurement	Description	Measurement Unit
Total coding data	Indicates the total logical size of all data chunks in the storage pool which are subject to erasure encoding.	GB
Total coded Data	Indicates the total logical size of all erasure-encoded chunks in the storage pool.	GB
Coded	Indicates the percent of data in the storage pool that is erasure encoded. Percent values display with three decimal places in the history chart for accurate plotting. Percent values display with two decimal points in the table, consistent with the format of the other values in the table.	Percentage
Coding rate	Indicates the rate at which data is being processed for erasure encoding.	MB/Sec