I'm having trouble with ESXi backup/restore performance.

My setup:

  • VMWare ESXi 5.0.0 on a HP ProLiant DL 360 G6, runnnig RAID 5 on a P410 SmartArray as SAS
  • QNAP Nas (QNAP TS-809U-RP NAS 8 bays 4USB) Connected over Gigabit

I try to copy a 200 GB file from the NAS to the Datastore. Currently, it will take 10 hours, so the speed is about 5 MB/s. This is very slow and I'm currently trying to figure out why it is this slow.

  1. I ran esxtop on my ESXi machine, it shows mainly an idle process,
  2. I ran the QNAP system resource monitor, it shows bandwith usage of +- 10 MB/s, no real CPU usage..
  3. So it seems the ESXi server is limiting the transfer speeds somehow. Another hint for this is that the performance -> disk graph stays almost exactly on 15MB/s

What is the preferred way to find out what is limiting the speeds?


I copy the file through the UI (vSphere Client), right click the datastore, click 'copy', and in the other datastore 'paste'

  • This is not a programming question, and belongs in ServerFault instead.
    – PhonicUK
    Aug 29, 2012 at 10:04
  • Flagged for request to move. Thanks for the comment btw. Aug 29, 2012 at 10:19

3 Answers 3


The fastest way to accomplish this transfer would be to use a higher-level tool like VMWare vCenter Converter to perform the migration. How are you running the copy? Drag-and-drop? Unix cp from the console?


ESXi is not a general purpose operating system and the management login mechanism you're using is a very-low-priority process not designed to be used in the way you are doing, it will also be 'going away' at some point in the future.

So basically use the interfaces/APIs that are designed for these purposes instead of pretending it's Linux and showhorning your own solution into place.


Check your P410 raid controller write cache. Vmware rely on hardware for caching.
You may need to add a BBU (Battery Backed Unit) on your controler to handle write back safely in case of power outtage.

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