Yellow Bricks

by Duncan Epping

6.6.1

Doing maintenance on a Two-Node (Direct Connect) vSAN configuration

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I was talking to a partner and customer last week at a VMUG. They were running a two node (direct connect) vSAN configuration and had some issues during maintenance which were, to them, not easy to explain. What they did is they placed the host which was in the “preferred fault domain” in to maintenance mode. After they placed that host in to maintenance mode the link between the two hosts for whatever reason failed. After they rebooted the host in the preferred host it connected back to the witness but at this point in time the connection between the hosts had not returned yet. This confused vSAN and that resulted in the scenario where the VMs in the secondary fault domain were powered off. As you can imagine an undesired effect.

This issue is solved in the near future in a new version of vSAN, but for those who need to do maintenance on a two-node (direct connect) configuration (or a full site maintenance in a stretched environment) I would highly recommend the following simple procedure. This will need to be done when doing maintenance on the host which is in the “preferred fault domain”:

  • Change the preferred fault domain
    • Under vSAN, click Fault Domains and Stretched Cluster.
    • Select the secondary fault domain and click the Mark Fault Domain as preferred for Stretched Cluster icon
  • Place the host in to maintenance mode
  • Do you maintenance

Fairly straight forward, but important to remember…

vSAN 6.6.1 Performance Diagnostics Demo

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I was playing in my lab this morning and figured I would record a demo of a new feature which is part of vSAN 6.6.1. The Performance Diagnostics feature is aimed to help those running benchmarks to optimize their benchmarks, or optimize their vSAN configuration to reach their expected goals. Note that it is a “cloud connected” feature, and in order to use this you need to participate in the Customer Experience Improvement Program. This however is enabled by default in the latest releases of vSphere. This means that data is send up to the VMware cloud, anonymous, then analyzed and the results are send back to the Web Client. Anyway, enough said, just watch the demo.

Unbalanced Stretched vSAN Cluster

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I had this question a couple of times the past month so I figured I would write a quick post. The question that was asked is: Can I have an unbalanced stretched cluster? In other words: Can I have 6 hosts in Site A and 4 hosts in site B when using vSAN Stretched Cluster functionality? Some may refer to this as asymmetric or uneven. Either way, the number of hosts in the two locations differ.

Is this supported? In short: Yes.

The longer answer: Yes you can do this, this is fully supported but you will need to keep your selected PFTT (Primary Failures To Tolerate), SFTT (Secondary Failures To Tolerate) and FTM (Failure Tolerance Method) in to account. If PFTT=1 and SFTT=2 and FTM=Erasure Coding (RAID5/6) then the minimum number of hosts per site is 6. You could however have 10 hosts in Site A while having 6 hosts in Site B.

Some may wonder why anyone would want this, well you can imagine you are running workloads which do not need to be recovered in the case of a full site failure. If that is the case you could stick these to 1 site. (You can set PFTT=0 and SFTT=1, which would result in this scenario for that particular VM.)

That is the power of Policy Based Management and vSAN, extremely flexibility and on a per VM/VMDK basis!

vSphere 6.5 U1 is out… and it comes with vSAN 6.6.1

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vSphere 6.5 U1 was released last night. It has some cool new functionality in there as part of vSAN 6.6.1 (I can’t wait for vSAN 6.6.6 to ship ;-)). There are a lot of fixes of course in 6.6.1 and U1, but as stated, there’s also new functionality:

  • VMware vSphere Update Manager (VUM) integration
  • Storage Device Serviceability enhancement
  • Performance Diagnostics in vSAN

So those using vSAN 6.2 who upgraded to vSphere 6.0 U3, here’s your chance to upgrade to get all vSAN 6.5 functionality, and more!

The VUM integration is pretty cool if you ask me. First of all, when there’s a new release the Health Check will call it out from now on. And on top of that, when you go to VUM then also things like async drivers will be taken in to consideration. Where you would normally have to slipstream drivers in to the image and make that image available through VUM, we now ensure that the image used is vSAN Ready! In other words, as of vSphere 6.5 U1 Update Manager is fully aware of vSAN and integrated as well. We are working hard to bring all vSAN Ready Node vendors on-board. (With Dell, Supermicro, Fujitsu and Lenovo leading the pack.)

Then there’s this feature called “Storage Device Serviceability enhancement”. Well this is the ability to blink the LEDs on specific devices. As far as I know, in this release we added support for HP Gen 9 controllers.

And last but not least: Performance Diagnostics in vSAN. I really like this feature. Note that this is all about analyzing benchmarks. It is not (yet?) about analyzing steady state. So in this case you run your benchmark, preferably using HCIBench, and then analyze it by selecting a specific goal. Performance will be analyzed using “cloud analytics”, and at the end you will get various recommendations and/or explanations for the results you’ve witnessed. These will point back to KBs, which in certain cases will give you hints how to solve your (if there is) bottleneck.

Note that in order to use this functionality you need to join CEIP (Customer Experience Improvement Program), which means that you will upload info in to VMware. But this by itself is very valuable as it allows our developers to solve bugs / user experience issues and getting a better understanding of how you use vSAN. I spoke with Christian Dickmann on this topic yesterday as he tweeted the below, and he was really excited, he said he had various fixes going in the next vSAN release based on the current data set. So join the program!

For those how can’t wait, here’s the release notes and downloads links:

Oh and before I forget, there’s new functionality in the H5 Client for vCenter in 6.5 U1. As mentioned on this vSphere blog: “Virtual Distributed Switch (VDS) management, datastore management, and host configuration are areas that have seen a big increase in functionality”. And then some of the “max config” items had a big jump. 50k powered on VMs for instance is huge:

  • Maximum vCenter Servers per vSphere Domain: 15 (increased from 10)
  • Maximum ESXi Hosts per vSphere Domain: 5000 (increased from 4000)
  • Maximum Powered On VMs per vSphere Domain: 50,000 (increased from 30,000)
  • Maximum Registered VMs per vSphere Domain: 70,000 (increased from 50,000)

That was it for now!