I am trying to installing a server which will contain my virtual servers.

Initially I installed the ESXi 5.5 U2 with IBM Customization (it is a System x 3250 M4 server)

I have to move some virtual machines from an old Esxi host (ESXi 5.1)

I am using VMX Explorer to do this (Old Esxi -> Storage Server -> New Esxi) But it has been impossible to do, because the transfer rates to the new server are too slow (< 1 MB/s).

Then I installed an older version of Esxi (4.1 U2 with IBM Customization), where transfer rates were acceptable according to my network environment (5 ~ 10 MB/s), but the restored VM was unusable because it was created with a newer version. Also, having a very old version of this software is insecure.

So I don't know what is happening, I read around the internet and a possible solution could be upgrading the RAID controller (it has a ServeRaid H1110) because ESXi does not use software cache for I/O operations, but it seems it is a software problem. Perhaps the 4.1 did use software cache, I could not confirm that.


I'm not familiar with VMX Explorer, but VMWare deliberately and artificially cripples the bandwidth available to tools like scp over any management interfaces, so I suspect it is probably using something like that to transfer the files between the hosts.

Don't bother spending any money on hardware for this. Instead use an approved method of transferring the VM's between hosts. Something like Veeam Backup Free can do this.


I'm not familiar with VMX Explorer, but I've used Vmware vCenter Converter before and it worked quite well. The converter is a free download from Vmware and it also let's you to customize your VM during the migration, so you may consider using it instead.

  • Thank you for your answer. I also tried this tool and the transfer rate was the same (< 1MB/s) – Pablo Nov 24 '15 at 21:25
  • @Pablo Hmm, that is odd. VMWare Converter does not usually get the same deliberate speed cripple that scp gets... – Mark Henderson Nov 24 '15 at 22:59

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