Yellow Bricks

by Duncan Epping

Virtual SAN

Can I still provision VMs when a vSAN Stretched Cluster site has failed? Part II

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3 years ago I wrote the following post: Can I still provision VMs when a VSAN Stretched Cluster site has failed? Last week I received a question on this subject, and although officially I am not supposed to work on vSAN in the upcoming three months I figured I could test this in the evening easily within 30 minutes. The question was simple, in my blog I described the failure of the Witness Host, what if a single host fails in one of the two “data” fault domains? What if I want to create a snapshot for instance, will this still work?

So here’s what I tested:

  • vSAN Stretched Cluster
  • 4+4+1 configuration
    • Meaning, 4 hosts in each “data site” and a witness host, for a total of 8 hosts in my vSAN cluster
  • Create a VM with cross-site protection and RAID-5 within the location

So I first failed a host in one of the two data sites. When I fail the host, the following is what happens when I create a VM with RAID-1 across sites and RAID-5 within a site:

  • Without “Force Provisioning” enabled the creation of the VM fails
  • When “Force Provisioning” is enabled the creation of the VM succeeds, the VM is created with a RAID-0 within 1 location

Okay, so this sounds similar to the originally described scenario, in my 2016 blog post, where I failed the witness. vSAN will create a RAID-0 configuration for the VM. When the host returns for duty the RAID-1 across locations and RAID-5 within each location is then automatically created. On top of that, you can snapshot VMs in this scenario, the snapshots will also be created as RAID-0. One thing to mind is that I would recommend removing “force provisioning” from the policy after the failure has been resolved! Below is a screenshot of the component layout of the scenario by the way.

I also retried the witness host down scenario, and in that case, you do not need to use the “force provisioning” option. One more thing to note. The above will only happen when you create a RAID configuration which is impossible to create as a result of the failure. If 1 host fails in a 4+4+1 stretched cluster you would like to create a RAID-1 across sites and a RAID-1 within sites then the VM would be created with the requested RAID configuration, which is demonstrated in the screenshot below.

Part 2: Is VSA the future of Software Defined Storage? (Customer use case)

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About 6.5 years ago I wrote this blog post around the future of Software-Defined Storage and if the VSA (virtual storage appliance) is the future for it. Last week at VMworld a customer reminded me of this article. Not because they read the article and pointed me back at it, but because they implemented what I described in this post, almost to the letter.

This customer had an interesting implementation, which kind of resembles the diagram I added to the blog post, note I added a part to the diagram which I originally left out but had mentioned in the blog (yes that is why the diagram looks like it is ancient… it is):

I want to share with you what the customer is doing because there are still plenty of customers that do not realize that this is supported. Note that this is supported by both vSAN as well as VMware Cloud Foundation, providing you a future proof, scalable, and flexible full-stack HCI architecture which does not need to be implemented in a rip and replace approach!

This customer basically leverages almost all functionality of our Software-Defined Storage offering. They have vSAN with locally attached storage devices (all NVMe) for certain workloads. They have storage arrays with vVols enabled for particular workloads. They have a VAIO Filter Driver which they use for replication. They also heavily rely on our APIs for monitoring and reporting, and as you can imagine they are a big believer in Policy-Based Management, as that is what helps them with placing workloads on a particular type of storage.

Now you may ask yourself, why on earth would they have vSAN and vVols sitting next to each other? Well, they had a significant investment in storage already, the storage solution was fully vVols capable and when they started using vSAN for certain projects they simply fell in love with Storage Policy-Based Management and decided to get it enabled for their storage systems as well. Even though the plan is to go all-in on vSAN over time, the interesting part here, in my opinion, is the “openness” of the platform. Want to go all-in on vSAN? Go ahead! Want to have traditional storage next to HCI? Go ahead! Want to use software-based data services? Go ahead! You can mix and match, and it is fully supported.

Anyway, just wanted to share that bit, and figured it would also be fun to bring up this 6.5 years old article again. One more thing, I think it is also good to realize how long these transitions tend to take. If you would have asked me in 2013 when we would see customers using this approach my guess would have been 2-3 years. Almost 6.5 years later we are starting to see this being seriously looked at. Of course, platforms have to mature, but also customers have to get comfortable with the idea. Change simply takes a lot of time.

Joined GigaOm’s David S. Linthicum on a podcast about cloud, HCI and Edge.

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A while ago I had the pleasure to join David S. Linthicum from GigaOm on their Voices in Cloud Podcast. It is a 22 minute podcast where we discuss various VMware efforts in the cloud space, edge computing and of course HCI. You can find the episode here, where they also have the full transcript for those who prefer to read instead of listen to a guy with a Dutch accent. It was a fun experience for sure, I always enjoy joining podcast’s and talking tech… So if you run a podcast and are looking for a guest, don’t hesitate to reach out!

Of course you can also find Voices in Cloud on iTunes, Google Play, Spotify, Stitcher, and other platforms.

Project nanoEDGE aka tiny vSphere/vSAN supported configurations!

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A few weeks ago VMware announced Project nanoEDGE on their blog virtual blocks. I had a whole bunch of questions the following days from customers and partners interested in understanding what it is and what it does. I personally prefer to call project nanoEDGE “a recipe”. In the recipe, it states which configuration would be supported for both vSAN as well as vSphere. Lets be clear, this is not a tiny version of VxRail or VMware Cloud Foundation, this is a hardware recipe that should help customers to deploy tiny supported configurations to thousands of locations around the world.

Project nanoEDGE is a project by VMware principal system engineer Simon Richardson. The funny thing is that right around the time Simon started discussing this with customers to see if there would be interest in something like this, I had similar discussions within the vSAN organization. When Simon mentioned he was going to work on this project with support from the VMware OCTO organization I was thrilled. I personally believe there’s a huge market for this. I have had dozens of conversations over the years with customers who have 1000s of locations and are currently running single-node solutions. Many of those customers need to deliver new IT services to these locations and the requirements for those services have changed as well in terms of availability, which makes it a perfect play for vSAN and vSphere (with HA).

So first of all, what would nanoEDGE look like?

As you can see, these are tiny “desktop alike” boxes. These boxes are the Supermicro E300-9D and they come in various flavors. The recipe currently explains the solution as 2 full vSAN servers and 1 host which is used for the vSAN Witness for the 2 node configuration. Of course, you could also run the witness remotely, or even throw in a switch and go with a 3 node configuration. The important part here is that all used components are on both the vSphere as well as the vSAN compatibility guide! The benefit of using the 2-node approach is the fact that you can use cross-over cables between the vSAN hosts and avoid the cost of a 10GbE Switch as a result! So what is in the box? The bill of materials is currently as follows:

  • 3x Supermicro E300-9D-8CN8TP
    • The box comes with 4x 1GbE NIC Port and 2x 10GbE NIC Port
    • 10GbE can be used for direct connect
    • It has an Intel® Xeon® processor D-2146NT – 8 cores
  • 6 x 64GB RAM
  • 3 x PCIe Riser Card (RSC-RR1U-E8)
  • 3 x PCIe M.2 NVMe Add on Card (AOC-SLG3-2M2)
  • 3x Capacity Tier – Intel M.2 NVMe P4511 1TB
  • 3x Cache Tier – Intel M.2 NVMe P4801 375GB
  • 3x Supermicro SATADOM 64GB
  • 1 x Managed 1GbE Switch

From a software point of view the paper lists they tested with 6.7 U2, but of course, if the hardware is on the VCG for 6.7 U3 than it will also be supported to run that configuration. Of course, the team also did some performance tests, and they showed some pretty compelling numbers (40.000+ read IOPS and close to 20.000 write IOPS), especially when you consider that these types of configurations would usually run 15-20 VMs in total. One thing I do want to add, the bill of materials lists M.2 form factor flash devices, this allows nanoEdge to avoid the use of the internal unsupported AHCI disk controller, this is key in the hardware configuration! Do note, that in order to fit two M.2 devices in this tiny box, you will need to also order the listed PCIe Riser Card and the M.2 NVMe add on card, William Lam has a nice article on this subject by the way.

There are many other options on the vSAN HCL for both caching as well as capacity, so if you prefer to use a different device, make sure it is listed here.

I would recommend reading the paper, and if you have an interest in this solution please reach out to your local VMware representative for more detail/help.

2 node direct connect vSAN and error “vSphere HA agent on this host could not reach isolation address”

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I’ve had this question over a dozen times now, so I figured I would add a quick pointer to my blog. What is causing the error “vSphere HA agent on this host could not reach isolation address” to pop up on a 2-node direct connect vSAN cluster? The answer is simple, when you have vSAN enabled HA uses the vSAN network for communication. When you have a 2-node Direct Connect the vSAN network is not connected to a switch and there are no other reachable IP addresses other than the IP addresses of the vSAN VMkernel interfaces.

When HA tries to test if the isolation address is reachable (the default gateway of the management interface) the ping will fail as a result. How you can solve this is simply by disabling the isolation response as described in this post here.