How to configure parallel processes in NXPowerLite Server

By default, NXPowerLite Server runs two optimizers in parallel, meaning it compresses two files at the same time. You can adjust this setting to either speed up the overall compression cycle (by increasing the number) or reduce system resource usage (by decreasing it).

This guide covers how changing the number of parallel processors on your system affects performance and how to monitor your system to ensure you aren't hitting hardware bottlenecks.

This preference was introduced in NXPowerLite Server 11. For older versions see the section Configure Parallel processing v10 or lower

Choosing the right number of parallel processes (and avoiding bottlenecks)

While the default is set to 2 concurrent optimizers, you may be tempted to increase this to heavily utilize your server's CPU. In our testing, increasing the value to 4 can yield good results, but going higher often introduces diminishing returns due to hardware bottlenecks—specifically Disk I/O.

Why Disk I/O becomes the bottleneck

The way NXPowerLite achieves deep compression is inherently read/write intensive. For modern Office documents (which are actually zip archives) or PDFs, the software must read the entire original file, extract its components to a temporary location on the disk, compress the individual images and assets, write a brand new optimized file, and finally swap it with the original.

When you run multiple optimizers concurrently, the server is doing this heavy extraction and rewriting process for multiple files simultaneously. The storage drive's read/write heads (or NVMe queues) must rapidly jump between different sectors to serve multiple active threads. If the disk cannot keep up, the CPU threads end up in an "I/O Wait" state—meaning your processor is sitting idle while waiting for the disk to finish reading or writing data. At this point, adding more optimizers will actually slow down the overall run.

Verifying the concurrently-running optimizers

Each active parallel process thread launches a separate instance of the Optimizer.exe process. You can view these to confirm your settings have taken effect:

1. Open Task Manager and navigate to the Details tab.

2. Sort the list by name and look for Optimizer.exe.

3. You should see multiple instances matching your configured number.

Note: Optimizer.exe only runs while it is actively optimizing a file and exits once complete. Therefore, the number of visible processes will fluctuate as files finish and new ones are picked up from the queue.

How to monitor CPU and Disk I/O 

If you increase the concurrent parallel processes, we highly recommend monitoring your system to ensure the disk isn't choking.

• Monitoring CPU (Task Manager): Open Task Manager and go to the Performance tab, then select CPU. If your CPU is constantly pegged at 100%, you have maximized your processor's capabilities and should not add more processes.

• Monitoring Disk I/O (Resource Monitor): While Task Manager gives a high-level view of disk active time, Windows Resource Monitor provides better detail for I/O bottlenecks.

  1. Open the Start menu, type resmon, and hit Enter to open Resource Monitor.

  2. Go to the Disk tab.

  3. Look at the Processes with Disk Activity panel and locate your Optimizer.exe instances to see their Read/Write Bytes per second.

  4. Most importantly, look at the Storage panel at the bottom, specifically the Disk Queue Length column. If this number is consistently high (e.g., above 2-3 per physical drive), your disk is overwhelmed by the parallel read/write requests, and you should scale back the number of optimizers.