Yellow Bricks

by Duncan Epping

8.0

New book: VMware vSAN 8.0 U1 Express Storage Architecture Deep Dive!

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We already gave some hints on twitter, and during an episode of the Unexplored Territory podcast, but here it finally is… The new book, the VMware vSAN 8.0 U1 Express Storage Architecture Deep Dive! It has been a year since we released the vSAN 7.0 U3 Deep Dive book, and with this brand new vSAN architecture being introduced in vSAN 8.0 we figured it was time to do a full overhaul of the book as well. Mind you, this new book purely deals with the Express Storage Architecture, aka vSAN ESA. This also means that some of the features which are not supported by ESA are not discussed in this book, for that you will need to buy the vSAN 7.0 U3 Deep Dive book, which covers OSA. Another big change is that we brought in a third author, we asked our good friend Pete Koehler to contribute to the book. Pete had done reviews of previous books, and considering the amount of material he produced for VMware Tech Marketing for vSAN (and ESA specifically) it made a lot of sense to bring him in!

VMware’s vSAN has rapidly proven itself in environments ranging from hospitals to oil rigs to e-commerce platforms and is the market leader in the hyperconverged space. Along the way, the world of IT has rapidly changed, not just from a software point of view, but also from a hardware perspective. With vSAN 8.0 VMware brought a new architecture to market called vSAN Express Storage Architecture (ESA). This architecture is highly optimized for today’s world of datacenter resources, be it CPU, memory, networking, or NVMe based flash storage.

The authors of the vSAN Deep Dive have thoroughly updated their definitive guide to this transformative technology. Writing for vSphere administrators, architects, and consultants, Cormac Hogan, Duncan Epping , and Pete Koehler explain what vSAN ESA is, why the architecture has changed, what it now offers, and how to gain maximum value from it. The book offers expert insight into preparation, installation, configuration, policies, provisioning, clusters, architecture, and more. You’ll also find practical guidance for using all data services, stretched clusters, two-node configurations, and cloud-native storage services.

Although we pressed publish on Tuesday, sometimes it takes a while before the book is available in all Amazon stores, but it should just trickle down in the upcoming 24-48 hours. The book is priced at 9.99 USD for the ebook and 29.99 USD for a paper copy, and is sold through Amazon only. Get it while it is hot, and we would appreciate it if you would use our referral links and leave a review when you finish it. Thanks for the support, and we hope you will enjoy it!

Of course, we also have the links to other major Amazon stores:

vSAN ESA ReadyNode configurations are more flexible than you think!

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I had a discussion at the Dutch VMUG yesterday about the ReadyNode configurations for vSAN ESA. The discussion was about how difficult it was to select a host and customize it. It was then that I realized that most people hadn’t noticed yet that there is an easier method (or lifehack as my kids would say) when it comes to selecting your server model. How does that work? Well, let me show you!

First, let’s take a look at the vSAN ESA ReadyNode Hardware Guidance Table. The table below shows you what the node capacity is for each profile from a storage, CPU, memory, and networking perspective.

Now if you look at the table you will see that as the “profile” number goes up, so does the capacity for each of the various components. This is actually what provides you with a lot of flexibility in my opinion. If we take Dell as an example, but the same applies for most vendors on the current list, and we select “vSAN-ESA-AF2” and look at the list of options we see the following:

  • PowerEdge R650
  • PowerEdge R6515
  • PowerEdge R750
  • PowerEdge R7515

Now, if we look at “vSAN-ESA-AF8” next, which is the highest profile, we see that we only can pick 1 server model, which happens to be the PowerEdge R750. If we then look at the difference between the hosts selected for each profile a few things stand out:

  • vSAN-ESA-AF2 has an Intel Xeon Silver 4314, while vSAN-ESA-AF8 has a Platinum 8358
  • vSAN-ESA-AF2 has 512GB, while vSAN-ESA-AF8 has 1024GB
  • vSAN-ESA-AF2 a 25Gbps NIC, while vSAN-ESA-AF8 has a 100Gbps NIC
  • vSAN-ESA-AF2 has five 3.2TB NVMe devices while vSAN-ESA-AF8 has twenty-four 3.2TB devices

Now if I look at the KB article which explains what you can, and cannot change, something stands out, most of the components can be modified/customized. For instance, for CPU you can go to a higher core count and/or higher base clock speed! For memory, you can go up, same for storage devices (as long as you stay within supported limits), etc etc.

In other words, what is the difference between a vSAN-ESA-AF2 and a vSAN-ESA-AF8? Basically the expected workload, the performance, the capacity. This ultimately results in a different configuration. Nothing, at this point in time, stops you from selecting the “lowest” vSAN ReadyNode Profile and spec it as an “AF4”, “AF6” or “AF8” from a CPU stance, or from a storage/memory capacity point of view. If you want to have some more flexibility, try selecting a smaller profile, select the host type, and increase the resources/components where needed!

When you start exploring the options it may seem complex, but when you look more closely you will quickly realize that it actually isn’t that complex, and that it actually provides you with a lot of flexibility, as long as you stick to the rules and pick supported components!

vSAN ESA is using more CPU cycles than vSAN OSA?

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Over the last couple of weeks, I’ve had conversations with customers and partners who have been running performance benchmarks against both vSAN ESA and vSAN OSA. As you can imagine, people want to compare version 8 of OSA against version 8 of ESA, and that is completely fair. What I noticed though is that some of those customers came back with comments around CPU usage of vSAN OSA against ESA. The general comment we get is that vSAN ESA is using more CPU cycles than vSAN OSA.

When looking at it from a total number point of view, or CPU cycles consumed, it is very likely you will see vSAN ESA using more cycles than vSAN OSA. The question then typically arises why that is the case, as VMware (the vSAN team) has been claiming that vSAN ESA is much more efficient than vSAN OSA. To be fair, it is much more efficient. For instance data services like checksumming, encryption, and compression have moved to the top of the stack (as shown below) resulting in the fact that we don’t have to compress/encrypt data 3/4/5/6 times but can do it once at the source and then send it over the network to the destination.

Still, it leaves the question, why is more CPU capacity used? The answer is simple, you are pushing much more IO. We’ve seen customers easily reaching 4x the number of IOPS with ESA than with OSA. Even though ESA is more efficient, if you are pushing 4x (or more) the amount of IO then you will need to remember that those additional IOs also come at a cost, and that cost is CPU cycles to process them. So when you make a comparison, please compare apples to apples, and not apples to oranges.

The last thing I want to add, and hopefully I can share some data in the future, the use of RDMA with vSAN 8 ESA seems to have a significant impact on CPU usage, as in lower the amount of CPU required to produce the same results (or better results). So it is worth considering RDMA for sure when adopting vSAN 8 ESA!

What can I change about a vSAN ESA Ready Node?

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I’ve had half a dozen people asking about this over the past weeks, it really seems more and more people are at the point of adopting vSAN ESA (Express Storage Architecture. When they look at the various vSAN ESA Ready Node configurations what stands out is that the current list is limited in terms of server models and configurations. (https://vmwa.re/vsanesahcl)

The list is being updated every week, last week for instance Supermicro popped up as a Server vendor. Of course, Dell, HPe, and Lenovo had been on the list since day 1. When you select the vendor, the ready node type, and the model you will then have the option to select a number of things, but in most cases, you seem to be limited to “Storage Device” and “Number of Storage Devices”. This however does not mean you cannot change anything. A knowledge base article has been released which describes what you can, and cannot change when it comes to these configurations! The KB article is listed on the vSAN ESA VMware Compatibility Guide list, but somehow it seems people don’t always notice the link. (Yes, I have asked the team to make the link more obvious somehow.)

Now when you look at the KB it lists what you can change, and what the rules are when it comes to making changes. For instance, you can change the CPU, but only for the same or higher core count and the same or higher base clock speed. For memory, you can increase the amount, and the same applies to storage capacity for instance. For storage it is even a bit more specific, you need to use the same make/model, so basically if the ReadyNode configuration lists a P5600 of 1.6TB, you can swap it for a P5600 of 3.2TB. We recently (May 20th 2023) had a change in support, and we now support the change of device model/make, as long as you follow the other guidelines mentioned in the KB. For instance, you can swap an Intel device for a Samsung, but that Samsung would need to be supported by the OEM vendor and needs to be the same (or higher) performance and endurance class. And of course the device needs to be certified for vSAN ESA: http://vmwa.re/vsanesahclc. Anyway, if you are configuring a Ready Node for ESA, make sure to check the KB so that you make supported changes!

Cross connecting vSAN Datastores with HCI Mesh in vSAN 8 OSA

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Yesterday I had a discussion internally on Slack about a configuration for a customer. The customer had multiple locations and had the potential to create various clusters within locations, or across locations. Now, as most of you know, I have been talking a lot about stretched clusters for the past decade. However, stretched clusters are not the answer to every problem. Especially not in situations where you end up with unbalanced configurations, or where you lack the ability to place a witness in a third location. Customers tend to gravitate towards stretched clusters as it provides them resiliency, and pooling of all resources even though they are across locations.

With vSAN when you have multiple clusters, you also have multiple vSAN Datastores. Having that separation of resources is typically appreciated. However, in some cases, customers prefer the flexibility of movement with limited overhead. Sure if you have multiple clusters you can simply Storage vMotion VMs from source cluster to destination cluster, but it does mean you need to move ALL the data with the VM, where in some cases you may not care where the data resides.

This is where HCI Mesh comes into play. With HCI Mesh you have the ability to mount a vSAN Datastore. Meaning, you have a “client” and a “server” cluster, and the client mounts the server. Within our documentation on core.vmware.com this is demonstrated as follows:

If you look at this diagram then the top two clusters are “client” clusters and the bottom one is the “server” cluster. This basically means that the “client” cluster consumed the datastore capacity from the “server” cluster. The above diagram however resulted in a bit of confusion as it does not show a situation where your client cluster can simultaneously be a server cluster. This is something I want to point out. You can create a true “mesh” with HCI Mesh! If you have two clusters, let’s say Cluster A and Cluster B, then you can mount the vSAN Datastore from Cluster A to Cluster B and the datastore from Cluster B to Cluster A. This is fully supported, and works great, as demonstrated in the below two screenshots. I tested this with vSphere/vSAN 8.0 OSA, but it is also supported with vSAN 7.0 U1 and up. Do note, vSAN ESA today does not support HCI Mesh just yet, hopefully it will in the near feature!


So before you decide how to configure vSAN, please look at all the capabilities provided, write down your requirements, and see what helps solving the challenges you are facing while meeting those requirements (in a supported way)!