File read over network very slow

Question

Im having an interesting problem with reading a large file (~400 mb) that's on a network drive. Orginally, I fed the full network address into a FileInfo and used the CopyTo function to transfer it to a local temp drive and then read it. This seems to work okay, its not slow but its not fast - just meh. The CopyTo function would get the computer running the program's network utilization consistantly up above 50%, which is pretty good.

In order to speed up the process I tried to read the network file directly into a Memory Stream to cut out the middle man so to speak. When I tried this (using the asynchronous copy pattern described here), it is hilariously slow. My network utilization never even tops 2% - its almost like something is throttling me. FYI, I watched my network utilization when directly copying the same file via windows explorer and it hit like 80-90%... not sure what's happening here. Below is the asynchronous copy code I used:

string line;
List<string> results = new List<string>();

Parser parser = new Parser(QuerySettings.SelectedFilters, QuerySettings.SearchTerms,
QuerySettings.ExcludedTerms, QuerySettings.HighlightedTerms);

byte[] ActiveBuffer = new byte[60 * 1024];
byte[] BackBuffer = new byte[60 * 1024];
byte[] WriteBuffer = new byte[60 * 1024];

MemoryStream memStream = new MemoryStream();
FileStream fileStream = new FileStream(fullPath, FileMode.Open, FileSystemRights.Read, FileShare.None, 60 * 1024, FileOptions.SequentialScan);

int Readed = 0;
IAsyncResult ReadResult;
IAsyncResult WriteResult;

ReadResult = fileStream.BeginRead(ActiveBuffer, 0, ActiveBuffer.Length, null, null);
do
{
    Readed = fileStream.EndRead(ReadResult);

    WriteResult = memStream.BeginWrite(ActiveBuffer, 0, Readed, null, null);
    WriteBuffer = ActiveBuffer;

    if (Readed > 0)
    {
        ReadResult = fileStream.BeginRead(BackBuffer, 0, BackBuffer.Length, null, null);
        BackBuffer = Interlocked.Exchange(ref ActiveBuffer, BackBuffer);
    }

    memStream.EndWrite(WriteResult);
}
while (Readed > 0);

StreamReader streamReader = new StreamReader(memStream);
while ((line = streamReader.ReadLine()) != null)
{
    if (parser.ParseResults(line))
    results.Add(line);
}

fileStream.Flush();
fileStream.Close();

memStream.Flush();
memStream.Close();

return results;

UPDATE As per the comments I just tried the following. It only had my network utilization at about 10-15%... why so low?

MemoryStream memStream = new MemoryStream();
FileStream fileStream = File.OpenRead(fullPath);

fileStream.CopyTo(memStream);

memStream.Seek(0, 0);
StreamReader streamReader = new StreamReader(memStream);

Parser parser = new Parser(QuerySettings.SelectedFilters, QuerySettings.SearchTerms,
QuerySettings.ExcludedTerms, QuerySettings.HighlightedTerms);

while ((line = streamReader.ReadLine()) != null)
{
if (parser.ParseResults(line))
results.Add(line);
}

Answer 1

I'm late to the party, but having had the same problem of low network utilization recently, after trying a lot of different implementations if found at last that a StreamReader with a large buffer (1MB in my case) increased the network utilization to 99%. None of the other options did make a significant change.