Rich Mingin (PLUG) on 17 Nov 2016 13:19:36 -0800

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Re: [PLUG] Linux networking really slow on copy

Coming in from a slightly different angle, and addressed a little more broadly, folks that are talking about "many times slower" networking on your VMs than on the hosts, are you using the e1000 driver? If so, that's part of your problem. Try switching to vmxnet3 on a few hosts, it's equally well supported on Linux, and it's paravirtualized, which removes a lot of overhead. I just slammed a pile of files back and forth between my desktop and a VM via rsync at line speed, I was seeing 110MB/s pretty consistently. Your VMs should perform within a percentage point or two of physical machines, if all the hardware is good and setup correctly.

Likewise, if you switch to the PVSCSI adapter on your guests, it takes a lot of VM IO overhead away as well.

On Thu, Nov 17, 2016 at 11:36 AM, Morgan Jones <> wrote:

When you get back to this: how confident are you about your cables?  Though not as bad as you describe I have seem significant problems with speed that turned out to just be crummy cables.


> On Nov 16, 2016, at 15:32, JP Vossen <> wrote:
> On 11/14/2016 12:31 PM, JP Vossen wrote:
>> I'm trying to copy about 3TB from a physical machine to a VM running on
>> Debian8 + VMware Workstation 10, and it's going badly.  I'm copying
>> 2,000+ MythTV files; half are the tiny PNG thumbnail pics and half are
>> *.mpg ranging up to a single 21G file.
> <snip>
> Thanks for the suggestions.
> Unfortunately some other issues have come up so this is stalled for now.  But to quickly follow-up with that I know so far:
> * Adding a switch into the cross-over cable mix helped a bit, but it was still not as expected.  That seemed to prevent going down to slow modem speeds, but speed still mostly hovered in the 10-25MB/s range despite the fact that both interfaces said "negotiated 1000baseT-FD flow-control, link ok".  Thanks Keith.
> * Using `vmware-mount` seems like it might work, thanks Lee, I'd forgotten about that.  That will take most of the VM overhear out.
> * I don't think I have any bad netmasks, but the VMware host ended up with 2 NICs bridging to the same LAN switch.  I can't think of a reason that would fail, but it might have caused some odd issues.  Things are not clear yet.
> Some other unrelated issues cropped up, resulting in me having to reboot almost everything, and I've got some other fish to fry right now.  When I have time to resume I'll look at rsync server writing directly to the mounted VMDK or possibly to the host disk and then copy into the VMDK. I'd like to get back to rsync because I've copied and re-copied the first 1TB or so of files a bunch of times now, as things fail and I kill it, and I'd like to stop doing that and only copy what's actually needed.
> Thanks again, and when I get back to this and solve it I'll send an update.
> Later,
> JP
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