Should it take 10 hours to export 32GBs of VMs in XenServer?



  • I wanted to backup 4 VMs using XenCenter. The VMs were suspended, then I selected them and went to the menu "VM" and then "Export".
    I exported them as vhd/ovf and sent them over the network to a Synology DS216+.

    The 4 VMs total are about 32GBs as backed up, but to break that down they are 1.8GB, 8.7GB, 6.2GB, and 17.6GB after backup.

    I know for a fact the 1.8GB VM backed up in only a minute or two. And I'm pretty sure the 8 and 6 gig VMs backed up relatively quickly as well. I think it hung up on the larger 17gb one for reasons I can't explain.

    I opened the backup folder shortly after starting the backup process and the 6 and 8 were already done. I then kept an eye on the folder for the rest of the day as the 17gb slowly grew in size for hours on end.

    What could be the reason for this?

    All the VMs use just one VD with a single partition. The only thing I can think of is that the 17GB backup happens to be a VM with the largest VD of about 2TB. It's not using all that space by any means, but that must be part of the issue somehow?


  • Service Provider

    If you are on an older version of XS, like XS 6.5, then yes, this is expected as it is a known performance issue with the platform around that time. This has been addressed in more recent releases.



  • This is still a problem on my 7.1 installation. Just tried exporting a 100GB vm, max speed 17MB/s, avg speed 15MB/s.
    Maybe it is because i upgraded from 6.1>6.2>6.5>7.1 over the last year or so. I havent tried export in a long time as it isnt something we need to do very often.



  • You can try exporting directly from XenServer but I believe you can only export in XVA format when done in CLI.



  • I just don't know why the backup that is 8GB was done in a number of minutes but the one that is 17GB took 9 hours. That's like an exponential increase!

    I plan on upgrading XS which is why I'm exporting the VMs in the first place. I hope the new file system layout of XS helps fix this.



  • You know, I haven't really looked back into it, but I noticed that my servers just don't have the proper speed at all in XS.

    I wonder if it is some sort of network driver issue.

    Have any of you ever tested throughput on your XS VMs? I haven't had a chance to do it, but it might be interesting.



  • @BRRABill I've run a number of iperf tests, and get the 850 to 920 mbps I'd expect from a gigabit network. There is something really wrong with exports in XenServer 6.X



  • @travisdh1

    Yeah I just never circled back around to it.

    I have to put that on my to-do list.



  • I get great bandwidth for all XS ops except import/export. Migrating vms/storage is almost always 100+MBps



  • The import / export functionality is supposed to be greatly improved in XS 7.1.



  • 10 hours for 32gb . . . . seems excessive even for the poorer performance of 6.5.


  • Service Provider

    @DustinB3403 said in Should it take 10 hours to export 32GBs of VMs in XenServer?:

    10 hours for 32gb . . . . seems excessive even for the poorer performance of 6.5.

    Good morning, where have you been?



  • @scottalanmiller New job has had me busy.




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