[BUG] Core 15x slower reading blobs than Framework

Describe the bug I am seeing the v12 Blobs library taking 45 seconds to read a blob via netcore that the same library can read in 3 seconds in Net4.7

Expected behavior I would expect core to be at least as fast as framework

Actual behavior (include Exception or Stack Trace) Framework is 15x faster than core. Framework appears to have requests active in parallel, core seems to serialise 16kb chunks.

To Reproduce Run the following code (obviously providing a connection string for a premium blob) in both core and framework

using System.Diagnostics;
using Azure.Storage.Blobs;
using Azure.Storage.Blobs.Models;

 

namespace BlobTest
{
  class Program
  {
    static void Main(string[] args)
    {
      Stopwatch sw = Stopwatch.StartNew();
      BlobClient blobClient = new BlobClient(new Uri( <insert premium blob address here> ));
      int toRead = 500 * 1024 * 1024;
      byte[] byteBuffer = new byte[toRead];
      Azure.Response<BlobDownloadInfo> response = blobClient.Download(new Azure.HttpRange(0,toRead));
      using (BlobDownloadInfo result = response.Value)
      {
        int followOns = 0;
        long read = result.ContentLength;
        long read2 = result.Content.Read(byteBuffer, 0, byteBuffer.Length);
        while (read2 < read)
        {
            ++followOns;
            long read3 = result.Content.Read(byteBuffer, (int)read2, byteBuffer.Length - (int)read2);
            read2 += read3;
            Debug.Assert(read3 > 0, "Failed to read blob");
        }
        sw.Stop();
        Console.WriteLine($"Read {toRead} in {sw.ElapsedMilliseconds}ms {followOns} followOns");
      }
    }
  }
}

Environment:

• Azure.Storage.Blobs 12.6.0
• Comparing Net Framework 4.7.2 and dotnetcore 3.1.301
• VS2019 16.6.2 Running on Azure VM D4sv3 with accelerated networking connecting to a premium block storage account in the same region (West Europe)

[jsquire]

Thank you for your feedback. Tagging and routing to the team best able to assist.

[jaschrep-msft]

Closing to favor #17305 as the solution to this situation.