How Do I Set the Number of Concurrent Processes for Linux File-Level Migrations?

Overview

You can set the maximum number of processes that the SMS-Agent can start concurrently (1 to 4) when migrating and synchronizing files of a Linux source server. However, the number of processes that can actually be started depends on how well the source server performs and how many disks and partitions the source server has.

• Enabling concurrency consumes source server resources, especially disk I/O, bandwidth, and CPU resources. To prevent the services on the source server from being affected, before enabling this function, you can evaluate the impacts on source services or set resource limits for the SMS-Agent.
• If the migration bandwidth from the source server to the target server is less than 300 Mbit/s, you are not advised to enable this function.

Calculating the Maximum Number of Concurrent Processes

The formula is:

Max. concurrent processes = Min. (Disks, Network bandwidth/Disk read or write performance, 4)

where

Disks is the number of disks to be migrated on the source server.

Network bandwidth is the network bandwidth between the source server and the target server. You can calculate the bandwidth by referring to How Do I Test the Network Between the Source and Target Servers Using iPerf?

Disk read or write performance is either the average disk read performance of the source server or the average disk write performance of the target server, whichever is smaller.

Assume that the migration involves four disks, the network bandwidth is 1,000 Mbit/s, the average read performance of the source server is 500 Mbit/s, the average write performance of the target server is 300 Mbit/s. In this example, we need to divide the network bandwidth by the average write performance of the target server (1,000 Mbit/s / 300 Mbit/s ≈ 3). That makes the three values for the formula, respectively, 4, 3 and 4, which means there can be 3 concurrent processes for this migration.

Setting the Maximum Number of Concurrent Processes

On the Configure Basic Settings page, set Migration Method to Linux file-level and Enable Concurrency to Yes, and specify Max. Concurrent Migrations and Max. Concurrent Syncs.