NTFS – Does File System Performance Decrease with Many Files in One Directory?

filesystemsntfswindows 7

I have heard that file system performance (on a NTFS partition) can start decreasing if the number of files in a single directory becomes very huge (eg : >= 10.000.000 items). Is it true ?

If true, what is the recommended maximum number of files in a single directory ?

EDIT:

About performance: I'm thinking about file operations inside that folder (read, write, create, delete) that could possibly get slow.

Best Answer

I answer my own question : Yes, it's definitely slower.

I wrote a C# Console Application that creates many empty files in a folder and then randomly access them. Here is the results :

10 files in a folder        : ~26000 operation/sec
1.000.000 files a in folder : ~6000 operation/sec

Here is source code :

List<string> files = new List<string>();

Console.WriteLine("creating files...");
for (int i = 0; i < 1000 * 1000; i++)
{
    string filename = @"C:\test\" + Guid.NewGuid().ToString();
    using (File.Create(filename));
    files.Add(filename);
}

Console.WriteLine("benchmark...");            
Random r = new Random();
Stopwatch sw = new Stopwatch();
sw.Start();

int count = 0;
while (sw.ElapsedMilliseconds < 5000)
{
    string filename = files[r.Next(files.Count)];
    string text = System.IO.File.ReadAllText(filename);
    count++;
}
Console.WriteLine("{0} operation/sec ", count / 5);
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