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Why is copying to a local UNC path so slow on my Windows 2008 R2 server? RRS feed

  • Question

  • I have a Windows 2008 R2 server named Server that runs a backup each night to an encrypted USB drive attached to the server. I shared the drive on the server as shown below and configured Windows Server Backup to backup to the local shared folder.

    • \\Server\Backup

    Everything worked well for several months with the backup speeds being about 1 GB/min (15 to 20 MB/s). At the beginning of this week, I noticed that the backup speeds reduced to 1 to 2 MB/s which resulted in the backup not completing before the encrypted disk was automatically dismounted.

    After much research and testing, I believe that I have narrowed down the cause of the issue to an issue writing data to the local UNC path of \\Server\Backup as shown by comparing the following tests.

    Test 1

    • c:> copy largefile h:\

    The above DOS command copies the file to the encrypted drive mounted at h:\ quickly.

    Test 2

    • c:> copy largefile \\Server\Backup

    The above DOS command copies the data to the same location but was 33x slower that the Test 1 DOS command.

    I duplicated the above results using the xcopy command instead of the copy command but could not duplicate the above results on my Windows 7 computer. On my Windows 7 computer, the two versions of the copy performed the same.

    The following are some additional observations:

    • If I change the backup location to an external UNC like \\Sever2\Backup, everything works well.
    • After repeatedly running Windows Server Backup after make changes such as restarting the server and tweaking the NIC parameters, the backup will all of a sudden start backing up at the normal speed but this will only last for about an hour before it reduces back to the slow backup speed.
    Tuesday, November 13, 2018 1:59 AM

Answers

  • I now believe that defective Western Digital Passport drives were the root cause of this issue.
    • Marked as answer by Reed Elliott Wednesday, June 12, 2019 1:03 AM
    Wednesday, June 12, 2019 1:03 AM

All replies

  • I am researching your question ,thanks for your waiting.

    Please remember to mark the replies as answers if they help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

    Tuesday, November 13, 2018 3:25 PM
  • I don't know the root cause of the issue but deleting the share, restarting the computer and then recreating the share resolved the issue.
    Tuesday, November 27, 2018 10:29 AM
  • thanks for your feedback .You can enter eventvwr and look if there are related error log .

    Please remember to mark the replies as answers if they help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

    Friday, November 30, 2018 3:04 PM
  • Most likely it was a server resources issue
    Friday, November 30, 2018 3:07 PM
  • I now believe that defective Western Digital Passport drives were the root cause of this issue.
    • Marked as answer by Reed Elliott Wednesday, June 12, 2019 1:03 AM
    Wednesday, June 12, 2019 1:03 AM