Forcing VMs to use the Flexible Network Adapter

One of my customers uses the Sophos UTM virtual appliance as a firewall/router.  It was originally set up as an Astaro version 8 virtual appliance and has been upgraded in place since then.  When that appliance was first made available, it used the Flexible network adapter by default, although the recommendation now is to use vmxnet3 for better performance.  Unfortunately, during the upgrade process, this change never went into place.

We’re trying to help this customer to resolve some performance problems and have identified that network adapter type as a potential bottleneck in their environment.  Before changing such a vital piece of a live environment, I decided to prototype it in the lab.  It turns out that Sophos no longer provides the virtual appliance, instead providing an ISO to install the software onto a VMware virtual machine.  No problem, I thought, and so I created the VM in my lab, aiming to match the appliance’s configuration settings.

As with so many other virtual appliances, this one’s OS type was “Other 2.6.x Linux (64-bit)” and so I built my VM to match.  Memory/vCPU count was no problem, but the network adapters gave me pause.  You can’t select Flexible for that OS type, yet the original appliance definitely had that adapter installed.  I knew that manually editing the VMX file for the VM was going to be the solution, but a bit of googleing didn’t reveal the appropriate syntax to use that particular adapter.  After a bit of head scratching, I realized the obvious solution – make a new DOS VM (which supports that adapter) and just compare the two VMX files myself.  Here’s what I saw:

On the UTM machine (with a e1000 adapter), the network adapter was defined like this:

ethernet3.present = "TRUE"
ethernet3.virtualDev = "e1000"
ethernet3.networkName = "VM-NetworkA"
ethernet3.addressType = "vpx"
ethernet3.generatedAddress = "00:50:56:b7:4b:ad"

On the DOS machine (with the flexible adapter), the network adapter was defined like this:

Ethernet0.present = "TRUE"
Ethernet0.networkName = "VM-NetworkA"
Ethernet0.addressType = "vpx"
Ethernet0.generatedAddress = "00:50:56:b7:3d:fe"

Notice that the line that defines the adapter type (the .virtualDev line) is just plain missing on the DOS machine.  It looks like the system defaults to a Flexible adapter when nothing else is specified… and if you actually want to use that adapter type for some reason, you just need to delete the statement that makes it another type.  So, I did the following:

1) Shutdown the UTM VM
2) Open the datastore browser that has my UTM VM and browse to the VM’s folder
3) Download the .vmx file onto my desktop
4) Edit the file in Wordpad
5) Delete the ethernet3.virtualDev = "e1000” line from the file and save
6) Upload the modified .vmx file back onto the datastore, overwriting the existing one (make a backup first!)
7) Find the existing VM in the inventory, right click on it and select Remove from Inventory
8) Right click on the modified .vmx file and select Add to Inventory and complete the wizard

And it worked!  What’s more, I was able to establish that the Flexible adapter only has between 1/4 and 1/5 the performance of the vmxnet3 adapter.  So, by simply removing the virtualDev line (that specifies the virtual device type) from that adapter in the VM’s configuration file, I was able to very easily force the VM to use the Flexible vmnic adapter type, even though it wasn’t available in the GUI for selection.

Comments

Post a Comment

Sorry guys, I've been getting a lot of spam recently, so I've had to turn on comment moderation. I'll do my best to moderate them swiftly after they're submitted,

Popular posts from this blog

Clone a Standard vSwitch from one ESXi Host to Another

One of my customers is standardizing the configurations on their HP C7000 enclosures (they've been set up at various sites by various administrators with varying involvement from the architecture team).  As such, we need to stand up some temporary resources so that we can take down the main enclosure for reconfiguration.  That's fine, we can easily ship a smaller enclosure to each site for temporary compute resources.  Some of the sites are using Standard vSwitches, so we need to be able to quickly copy the networking configuration over from their existing blades to these new, slightly different blades.  As I see it, we had 2 good options: 1) Capture a Host Profile with the desired vSwitch configuration.  Delete every other component of the Host Profile so that only the networking section is applied; design the new ESXi hosts so that the vSwitches'll work with the old vmnic-to-vswitch configurations. 2) Write a script to clone the vSwitch from ones ESXi host...
Read more

PowerShell Sorting by Multiple Columns

PowerShell's Sort-Object cmdlet is super useful, especially when preparing output for human consumption.  A few people have found my blog while looking for more information about its use, specifically while looking for how to sort by multiple columns (well, properties, technically).  I've never done so (much less written about it), so I hope those folks found answers elsewhere.  But, it got me curious... and it turns out that it's really easy. The Technet article on Sort-Object has the answer directly spelled out: just use commas to create a list of properties to sort by (in order to precedence).  Let's look at some examples!  First, prepare a variable with some good sortable data: $myData = get-eventlog System -newest 25 And then we can get to sorting!  Say you want to sort primarily by EntryType (Warning, Information, Error) and then by Source.  Easy-peasy: $myData | sort EntryType,Source How about if you want it to be in descending or...
Read more

Deleting Orphaned (AKA Zombie) VMDK Files

A problem that most Virtualization Administrators need to deal with is Orphaned VMDK files (or Zombie VMDK files, as some people call them).  These are Virtual Machine hard drive files that are just hanging out, taking up storage, but are attached to no VMs.  How can this happen?  Well, the most common way is when an administrator needs to delete a VMDK but isn't quite ready to commit... so, after pressing "remove", they select "remove from virtual machine" rather than "remove and delete files".  The intent is always good: "I want to be able to restore this if it turns out to be necessary... so I'll just come back and delete it next week if nothing breaks!"  But, of course, next week something else happens and the file doesn't get deleted.  After a little while, it turns into "which files did I rename, again?" and nothing seems to happen. So, how do you deal with these orphaned files?  Well, a few years ago I found a scrip...
Read more