How do I increase performance on the same single blob download for 3000 - 18,000 clients all downloading in a 5 minute range? (Can't use CDN because we need the files to be private with SAS). RRS feed

  • Question

  • Requirements:

    • We can't use CDN because the file or "blob" needs to be      private.  We’ll generate SAS keys on      all the simultaneous download requests.      
    • The files/blobs will be the encrypted exams uploaded 24 or 48 hours      before an Exam start time.
    • 3000 - 18,000 downloads at the same start time in a 5- 10 minute      window before the Exam start time. 
    • 172 – 1000 blobs.   Sizes (53 K Byte – 10 M byte )
    • We have a web service that verifies the students info, pin, exam      date/time are correct.   If correct, generates the URI & SAS.
    •      Azure site said only 480 Mbit/s for a single blob.   https://azure.microsoft.com/en-us/documentation/articles/storage-performance-checklist/#subheading16
    • But another part of Azure site mentions as high as 20,000 trans/sec      @ 20 Gbps if GRS enabled, 30 Gbps for LRS
    •    https://azure.microsoft.com/en-us/documentation/articles/storage-scalability-targets/      which I assume is for many different blobs per many clients.


    • Would snapshot of the blob help? 
      • I thought a snapshot is only helpful if you know the source blob       is being updated during a download?
    • Would premium help? 
      • I read premium just means it’s stored on a SSD for more $)  But we need more bandwidth and many clients hitting the same blob.
    • Would creating say 50 copies of the same Exam help? 
      • Then rotate each client browser through each copy of the file. 


    • Edited by shawn.yu Monday, July 6, 2015 5:25 PM
    Tuesday, June 30, 2015 7:50 PM

All replies

  • Hi Shawn,

    I see that your query has been replied to in StackOverflow.
    I hope that answers your query.
    Please let us know if you still require assistance with this.


    Wednesday, July 1, 2015 10:49 AM
  • I didn't get an answer on Stack overflow.  People were generous with ideas but they disagreed with each other.  I would like assistance from a Microsoft person. 

    - Is there other features of Azure we could use? 

    - Am I wrong about CDN not expireing files in 10 hours?  I saw they default expire in 7 day.

    - I tried CDN with SAS but the security failed because I was able to download the file without the SAS key.  or was I wrong in my CDN security setup?  We need to lock the file in CDN.  Only allowing someone to download if they have a valid SAS.

    Monday, July 6, 2015 2:11 PM