[windows] NTFS performance and large volumes of files and directories

I am building a File-Structure to host up to 2 billion (2^32) files and performed the following tests that show a sharp drop in Navigate + Read Performance at about 250 Files or 120 Directories per NTFS Directory on a Solid State Drive (SSD):

• The File Performance drops by 50% between 250 and 1000 Files.
• The Directory Performance drops by 60% between 120 and 1000 Directories.
• Values for Numbers > 1000 remain relatively stable

Interestingly the Number of Directories and Files do NOT significantly interfere.

So the Lessons are:

• File Numbers above 250 cost a Factor of 2
• Directories above 120 cost a Factor of 2.5
• The File-Explorer in Windows 7 can handle large #Files or #Dirs, but Usability is still bad.
• Introducing Sub-Directories is not expensive

This is the Data (2 Measurements for each File and Directory):

(FOPS = File Operations per Second)
(DOPS = Directory Operations per Second)

#Files  lg(#)   FOPS    FOPS2   DOPS    DOPS2
   10   1.00    16692   16692   16421   16312
  100   2.00    16425   15943   15738   16031
  120   2.08    15716   16024   15878   16122
  130   2.11    15883   16124   14328   14347
  160   2.20    15978   16184   11325   11128
  200   2.30    16364   16052   9866    9678
  210   2.32    16143   15977   9348    9547
  220   2.34    16290   15909   9094    9038
  230   2.36    16048   15930   9010    9094
  240   2.38    15096   15725   8654    9143
  250   2.40    15453   15548   8872    8472
  260   2.41    14454   15053   8577    8720
  300   2.48    12565   13245   8368    8361
  400   2.60    11159   11462   7671    7574
  500   2.70    10536   10560   7149    7331
 1000   3.00    9092    9509    6569    6693
 2000   3.30    8797    8810    6375    6292
10000   4.00    8084    8228    6210    6194
20000   4.30    8049    8343    5536    6100
50000   4.70    7468    7607    5364    5365

And this is the Test Code:

[TestCase(50000, false, Result = 50000)]
[TestCase(50000, true, Result = 50000)]
public static int TestDirPerformance(int numFilesInDir, bool testDirs) {
    var files = new List<string>();
    var dir = Path.GetTempPath() + "\\Sub\\" + Guid.NewGuid() + "\\";
    Directory.CreateDirectory(dir);
    Console.WriteLine("prepare...");
    const string FILE_NAME = "\\file.txt";
    for (int i = 0; i < numFilesInDir; i++) {
        string filename = dir + Guid.NewGuid();
        if (testDirs) {
            var dirName = filename + "D";
            Directory.CreateDirectory(dirName);
            using (File.Create(dirName + FILE_NAME)) { }
        } else {
            using (File.Create(filename)) { }
        }
        files.Add(filename);
    }
    //Adding 1000 Directories didn't change File Performance
    /*for (int i = 0; i < 1000; i++) {
        string filename = dir + Guid.NewGuid();
        Directory.CreateDirectory(filename + "D");
    }*/
    Console.WriteLine("measure...");
    var r = new Random();
    var sw = new Stopwatch();
    sw.Start();
    int len = 0;
    int count = 0;
    while (sw.ElapsedMilliseconds < 5000) {
        string filename = files[r.Next(files.Count)];
        string text = File.ReadAllText(testDirs ? filename + "D" + FILE_NAME : filename);
        len += text.Length;
        count++;
    }
    Console.WriteLine("{0} File Ops/sec ", count / 5);
    return numFilesInDir; 
}