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No performance gain after using CDN? RRS feed

  • Question

  • Hi, All

    I try to signup an azure account and then create a storage account for Blob, then I put a test file to a container.

    Then I enable the CDN for the storage account. However, the download speed is not very good, even worse that the original server.

    My file at Azure Cloud Server is https://datanumen.blob.core.windows.net/download/index.htm

    I create a CDN using Azure CDN Standard from Microsoft, the URL for the test file is https://datanumen.azureedge.net/download/index.htm

    I also create a CDN using Azure CDN Standard from Akamai, the URL for the test file is: https://datanumen1.azureedge.net/download/index.htm

    I even create a CDN using Azure CDN Standard from Verizon, the URL for the test file is https://datanumen2.azureedge.net/download/index.htm (This one is not available since the propagation usually completes within 90 minutes)

    I then test the download speed of the test file at https://tools.pingdom.com , download from South America, the results are:

    Original Cloud server speed: 2.11s
    CDN from MS: 2.37s
    CDN from Akamai: 2.34s

    So when using CDN, the speed is WORSE than the original server. There are no performance gain at all! Why?

    Thanks
    Tuesday, March 5, 2019 5:58 AM

Answers

  • Hi, 

    Here is a document which helps you to understand how caching works in Azure. 

    https://docs.microsoft.com/en-us/azure/cdn/cdn-how-caching-works

    If your request hits different POP server, then the performance would be the same. Next time when the request hits the same POP server, you can see significant improvements. 

    Regards, 

    Msrini

    • Marked as answer by tempc Saturday, March 16, 2019 2:50 AM
    Tuesday, March 5, 2019 10:39 AM

All replies

  • Hi, 

    I do see a lot of 404's when you try to access the site. The reason why you did get a good download speed is that those request with 404s are not cached. 

    Can you try adding a new static web page with an image and try using CDN to check the performance?

    Note: This is just for testing purpose. Once you get desired speed with Azure CDN with the new static page, you can fix those 404 and try again. 

    Regards, 

    Msrini

    Tuesday, March 5, 2019 7:15 AM
  • Hi,

    Thank you very much.

    To eliminate the effect of 404 errors, I change the test file to a big JPEG image(about 2MB) instead.

    Below is the test result(I use https://tools.pingdom.com to perform the test):

    Download From South America:

    US Dedicated Server: https://www.datanumen.com/temp/test.jpg 2.91s

    Azure:

    https://datanumen.blob.core.windows.net/download/test.jpg 1.82s

    https://datanumen.azureedge.net/download/test.jpg 2.38s

    https://datanumen1.azureedge.net/download/test.jpg 1.5s

    https://datanumen1.azureedge.net/download/test.jpg 2.03s


    Google:

    https://storage.googleapis.com/datanumen/test.jpg 498ms

    With Azure CDN, the fastest possible speed is 1.5s, about 20% faster than the original server, 100% faster than using the traditional dedicated server. This is an improvement. However, after comparing the speed with those of Google Cloud platform, it seems Google's speed is much better?


    • Edited by tempc Tuesday, March 5, 2019 10:24 AM
    Tuesday, March 5, 2019 9:11 AM
  • Thank you for providing the results. Can you let me know which tool you are using to test ?

    Also, can you do the test more than one time, because first time when you do the test, CDN will cache the request and for the second time when you try to access the same page and if it hits the same POP server, then you can see the improvements in speed. 

    Regards, 

    Msrini

    Tuesday, March 5, 2019 9:25 AM
  • Hi,

    I use https://tools.pingdom.com to perform the test.

    I also try to retest the file download. But it seems that with the Azure CDN, the result may be worse, for example:

    https://datanumen1.azureedge.net/download/test.jpg will increase from 1.5s to 2.1s

    While I do see a big decrease in the download time for Google. 

    https://storage.googleapis.com/datanumen/test.jpg will be 498ms for the first time and then 367ms for the second.

    The problem of Google is that it is not as easy as Azure. But it seems Google's performance is much better?

    Thanks

     

    Tuesday, March 5, 2019 10:31 AM
  • Hi, 

    Here is a document which helps you to understand how caching works in Azure. 

    https://docs.microsoft.com/en-us/azure/cdn/cdn-how-caching-works

    If your request hits different POP server, then the performance would be the same. Next time when the request hits the same POP server, you can see significant improvements. 

    Regards, 

    Msrini

    • Marked as answer by tempc Saturday, March 16, 2019 2:50 AM
    Tuesday, March 5, 2019 10:39 AM