How can you throttle file read/write speed to simulate slow I/O conditions?

Question

Anubhav Kumar · Answer

To throttle file read/write speed and simulate slow I/O conditions (e.g., for testing buffering, retry logic, or system behavior under disk pressure), you can implement manual throttling using techniques like:
1. Add Delays Between Chunks
Read or write the file in small chunks (e.g., 1 KB, 4 KB) and introduce a 
Thread.Sleep after each operation to simulate latency or reduced throughput.
Example: Throttled File Write
using System;
using System.IO;
using System.Text;
using System.Threading;
void ThrottledWrite(string path, byte[] data, int chunkSize = 1024, int delayMs = 100)
{
    using (var fs = new FileStream(path, FileMode.Create, FileAccess.Write))
    {
        int offset = 0;
        while (offset andlt; data.Length)
        {
            int bytesToWrite = Math.Min(chunkSize, data.Length - offset);
            fs.Write(data, offset, bytesToWrite);
            fs.Flush(); // optional but useful for simulating real I/O
            offset += bytesToWrite;
            Thread.Sleep(delayMs); // throttle speed
        }
    }
}
// Example usage
var data = Encoding.UTF8.GetBytes(new string('A', 10_000));
ThrottledWrite("slow_write.txt", data, 1024, 50);
Example: Throttled File Read
void ThrottledRead(string path, int chunkSize = 1024, int delayMs = 100)
{
    using (var fs = new FileStream(path, FileMode.Open, FileAccess.Read))
    {
        byte[] buffer = new byte[chunkSize];
        int bytesRead;
        while ((bytesRead = fs.Read(buffer, 0, buffer.Length)) andgt; 0)
        {
            // Process data (or just discard)
            Thread.Sleep(delayMs); // simulate slow read
        }
    }
}
2. Use async/await and
Task.Delay
For asynchronous throttling (non-blocking):
async Task ThrottledWriteAsync(string path, byte[] data, int chunkSize = 1024, int delayMs = 100)
{
    using (var fs = new FileStream(path, FileMode.Create, FileAccess.Write, FileShare.None, 4096, true))
    {
        int offset = 0;
        while (offset andlt; data.Length)
        {
            int bytesToWrite = Math.Min(chunkSize, data.Length - offset);
            await fs.WriteAsync(data, offset, bytesToWrite);
            await fs.FlushAsync();
            offset += bytesToWrite;
            await Task.Delay(delayMs); // async throttle
        }
    }
}
3. Use External Tools (Optional)
If you want system-wide or device-level throttling for more realistic testing:
Linux: Use tc, ionice, cgroups, or
fallocate with loop devicesWindows: Tools like Diskspd, HWiNFO, or virtualization tools to throttle I/O
Summary
Method
Suitable For
Blocking
Notes
Manual chunking + delay
Simple tests
Yes
Good for simulating I/O slowness
Async + Task.Delay
Async code paths
No
More realistic for web apps
External tools
System-level
N/A
Ideal for load or stress testing
and

forum

How can you throttle file read/write speed to simulate slow I/O conditions?

Ravi Vishwakarma

Can you answer this question?

1 Answers

1. Add Delays Between Chunks

Example: Throttled File Write

Example: Throttled File Read

2. Use `async/await` and `Task.Delay`

3. Use External Tools (Optional)

Summary

Liked By

Method	Suitable For	Blocking	Notes
Manual chunking + delay	Simple tests	Yes	Good for simulating I/O slowness
Async + `Task.Delay`	Async code paths	No	More realistic for web apps
External tools	System-level	N/A	Ideal for load or stress testing

forum

How can you throttle file read/write speed to simulate slow I/O conditions?

Ravi Vishwakarma

Can you answer this question?

1 Answers

1. Add Delays Between Chunks

Example: Throttled File Write

Example: Throttled File Read

2. Use async/await and Task.Delay

3. Use External Tools (Optional)

Summary

Liked By

2. Use `async/await` and `Task.Delay`