Yellow Bricks

by Duncan Epping

Various

Isolation Address in a 2-node direct connect vSAN environment?

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As most of you know by now when vSAN is enabled vSphere HA uses the vSAN network for heartbeating. I recently wrote an article about the isolation address and relationship with heartbeat datastores. In the comment section, Johann asked what the settings should be for 2-Node Direct Connect with vSAN. A very valid question as an isolation is still possible, although not as likely as with a stretched cluster considering you do not have a network switch for vSAN in this configuration. Anyway, you would still like the VMs that are impacted by the isolation to be powered off and you would like the other remaining host to power them back on.

So the question remains, which IP Address do you select? Well, there’s no IP address to select in this particular case. As it is “direct connect” there are probably only 2 IP addresses on that segment (one for host 1 and another for host 2). You cannot use the default gateway either, as that is the gateway for the management interface, which is the wrong network. So what do I recommend:

  • Disable the Isolation Response >> set it to “leave powered on” or “disabled” (depends on the version used
  • Disable the use of the default gateway by setting the following HA advanced setting:
    • das.usedefaultisolationaddress = false

That probably makes you wonder what will happen when a host is isolated from the rest of the cluster (other host and the witness). Well, when this happens then the VMs are still killed, but not as a result of the isolation response kicking in, but as a result of vSAN kicking in. Here’s the process:

  • Heartbeats are not received
  • Host elects itself primary
  • Host pings the isolation address
    • If the host can’t ping the gateway of the management interface then the host declares itself isolated
    • If the host can ping the gateway of the management interface then the host doesn’t declare itself isolated
  • Either way, the isolation response is not triggered as it is set to “Leave powered on”
  • vSAN will now automatically kill all VMs which have lost access to its components
    • The isolated host will lose quorum
    • vSAN objects will become isolated
    • The advanced setting “VSAN.AutoTerminateGhostVm=1” allows vSAN to kill the “ghosted” VMs (with all components inaccessible).

In other words, don’t worry about the isolation address in a 2-node configuration, vSAN has this situation covered! Note that “VSAN.AutoTerminateGhostVm=1” only works for 2-node and Stretched vSAN configurations at this time.

UPDATE:

I triggered a failure in my lab (which is 2-node, but not direct connect), and for those who are wondering, this is what you should be seeing in your syslog.log:

syslog.log:2017-11-29T13:45:28Z killInaccessibleVms.py [INFO]: Following VMs are powered on and HA protected in this host.
syslog.log:2017-11-29T13:45:28Z killInaccessibleVms.py [INFO]: * ['vm-01', 'vm-03', 'vm-04']
syslog.log:2017-11-29T13:45:32Z killInaccessibleVms.py [INFO]: List inaccessible VMs at round 1
syslog.log:2017-11-29T13:45:32Z killInaccessibleVms.py [INFO]: * ['vim.VirtualMachine:1', 'vim.VirtualMachine:2', 'vim.VirtualMachine:3']
syslog.log:2017-11-29T13:46:06Z killInaccessibleVms.py [INFO]: List inaccessible VMs at round 2
syslog.log:2017-11-29T13:46:06Z killInaccessibleVms.py [INFO]: * ['vim.VirtualMachine:1', 'vim.VirtualMachine:2', 'vim.VirtualMachine:3']
syslog.log:2017-11-29T13:46:06Z killInaccessibleVms.py [INFO]: Following VMs are found to have all objects inaccessible, and will be terminated.
syslog.log:2017-11-29T13:46:06Z killInaccessibleVms.py [INFO]: * ['vim.VirtualMachine:1', 'vim.VirtualMachine:2', 'vim.VirtualMachine:3']
syslog.log:2017-11-29T13:46:06Z killInaccessibleVms.py [INFO]: Start terminating VMs.
syslog.log:2017-11-29T13:46:06Z killInaccessibleVms.py [INFO]: Successfully terminated inaccessible VM: vm-01
syslog.log:2017-11-29T13:46:06Z killInaccessibleVms.py [INFO]: Successfully terminated inaccessible VM: vm-03
syslog.log:2017-11-29T13:46:06Z killInaccessibleVms.py [INFO]: Successfully terminated inaccessible VM: vm-04
syslog.log:2017-11-29T13:46:06Z killInaccessibleVms.py [INFO]: Finished killing the ghost vms

Have you read the vSphere Host Resources Deepdive book yet?

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Well if you haven’t read (or bought) the vSphere Host Resources Deepdive book yet then this may be worth your time. Rubrik and VMUG are giving away FREE ebook copies to everyone who simply registers. I just registered and got myself a nice PDF copy of the book. For those who haven’t heard about the book before read my review here. (Or check the reviews on Amazon, 4.9 out of 5 sounds solid to me.)

Anyway, what more can I cay then: download it now! 571 pages, in a single PDF, of pure deepdive awesomeness!

Extract embedded video file from Powerpoint on OSX

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I received a couple of presentations over the past weeks which had an embedded video file in it, but needless to say this article will handle all types of embedded files. I needed the source file but unfortunately the person who developed the demo video did not have it any longer. Latest versions of Powerpoint for Mac OSX don’t have the option to copy/paste the file somewhere else, there’s also no “right click save as” option unfortunately. So how do you grab this file?

Well according to the sources found on google it is simple, you rename the Powerpoint .PPTX file to zip and simply unzip it. I tried that, but my zip file then got unzipped to a zip.cpgz file. Which I then would try to unzip but again would lead to a zip file. Going around in circles. But there’s a solution for it. If simply double clicking after renaming doesn’t work, try the following procedure:

Open a terminal window:

  • To open Terminal, go to Applications > Utilities > Terminal
  • Go to the folder where the file is located, in my case Desktop/test 
    cd ~/Desktop/test
  • Unzip the file (my filename is presentation.pptx) 
    unzip presentation.pptx

If that doesn’t work, rename the presentation.pptx to presentation.zip and try the above procedure, of course with the correct file name!

Now you should see 3 folders in finder (docProps, _rels and ppt) and an additional file (.xml). If you go in to the folder “ppt” you will find a folder “media”. That folder will contain all media files, which includes pictures/photos/soundbites and your videos!



Which disk controller to use for vSAN

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I have many customers going through the plan and design phase for implementing a vSAN based infrastructure. Many of them have conversations with OEMs and this typically results in a set of recommendations in terms of which hardware to purchase. One thing that seems to be a recurring theme is the question which disk controller a customer should buy. The typical recommendation seems to be the most beefy disk controller on the list. I wrote about this a while ago as well, and want to re-emphasize my thinking. Before I do, I understand why these recommendations are being made. Traditionally with local storage devices selecting the high-end disk controller made sense. It provided a lot of options you needed to have a decent performance and also availability of your data. With vSAN however this is not needed, this is all provided by our software layer.

When it comes to disk controllers my recommendation is simple: go for the simplest device on the list that has a good queue depth. Just to give an example, the Dell H730 disk controller is often recommended, but if you look at the vSAN Compatibility Guide then you will also see the HBA330. The big difference between these two is the RAID functionality offered on the H730 and the cache on the controller. Again, this functionality is not needed for vSAN, by going for the HBA330 you will save money. (For HP I would recommend the H240 disk controller.)

Having said that, I would at the same time recommend customers to consider NVMe for the caching tier instead of SAS or SATA connected flash. Why, well for the caching layer it makes sense to avoid the disk controller. Place the flash as close to the CPU as you can get for low latency high throughput. In other words, invest the money you are saving on the more expensive disk controller in NVMe connected flash for the caching layer.

Don’t know why DRS is not balancing your cluster? DRS Dump Insight!

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I was just reading up and noticed the DRS Dump Insight solution. It is a SaaS based DRS Dump Analyzer which gives you details around why your cluster is not balanced, or why certain recommendations are not made. Especially the “what if” scenarios are cool if you ask me. You can take a dump and then using the whatif feature check out what would happen to your cluster if for instance all affinity rules were dropped. Or what would happen if the DRS migration threshold is changed, or some advanced settings are used.

You can find some more info about it here, and the SaaS tool here. I hope this will make it in to the product soon in the form of a “health check”… Very useful and insightful! Oh, if you can’t access the website, try it in “Incognito Mode”. Seems there are some issues with the certificate.