WilliamLam.com

Enhanced Linked Mode (ELM) vs Hybrid Linked Mode (HLM)

by // 2 Comments

In the last few weeks, albeit due to VMworld, I have seen a large number of inquiries from customers regarding the existing vCenter Enhanced Linked Mode (ELM) as it compares to the newly announced Hybrid Linked Mode (HLM) feature. In some cases, certain assumptions were being made based on what was initially announced and I think that also led to some confusion on what the future holds for both of these capabilities. Hopefully with this article, I can help clarify the differences between ELM and HLM and their respective use cases. I will also quickly touch upon some of the future thinkings for both of these features as they were discussed at several VMworld Sessions both in the US and Europe.

Disclaimer: Hopefully folks are familiar with the standard VMworld Disclaimer slide that is shown before any session which states features are subject to change and must not be included in contracts, purchase orders or sales agreement of any kind. I am sure many of you have memorized it by now, but this is a good time to re-iterate that point, especially as we talk about futures 🙂

Current

Lets start off by reviewing what we have today and explaining the differences between ELM and HLM.

[Read more...]

Uniquely identifying VMs in vSphere Part 3: Enhanced Linked Mode & Cross VC-vMotion

by // 7 Comments

Back in 2012, I had published two articles which provides details and guidance on how to uniquely identify a Virtual Machine for both a vSphere and/or vCloud Director environment. The primary use case for this information was for customers or partners who have developed their own provisioning solution which requires them to track their VM assets throughout their lifecycle, usually in some sort of configuration management database (CMDB).

Although these articles are almost 5 years old, the content is still very relevant today and I still continue to reference them both with customers, partners and even some of our internal R&D folks. Most recently, I had a question about whether the guidance in these article were still applicable or whether they would be impacted by some of the new VMware technologies and capabilities that had been introduced since writing those articles such as Enhanced Linked Mode (ELM) and Cross vCenter vMotion (xVC-vMotion).

[Read more...]

Maximum number of vCenter Servers per Single Sign-On (SSO) Domain

by // 9 Comments

This particular question and its variations have been raised quite a bit lately by our field and customers. For me, this was an opportunity to see if we can provide some additional clarification and help explain some of the nuances that may have been causing some of the confusion around the supported maximums for both vCenter Server and the Platform Services Controller (PSC).

In the vSphere 6.5 Configuration Maximum, there are three specific maximums that helps us answer our question on the maximum number of vCenter Servers per vCenter Single Sign-On (SSO) Domain. I will go through each of the maximums and provide some additional context that will help us derive the answer to our question.

The first is the "Linked vCenter Servers" which defines the maximum number of vCenter Servers that can be supported in an Enhanced Linked Mode (ELM) configuration. What is interesting about this particular maximum is that it actually answers the majority of our question. By definition, an ELM consists of a single SSO Domain. This then means that you can only have a maximum of 10 vCenter Servers per SSO Domain.

vCenter Server Maximum

Configuration Maximum
Linked vCenter Servers (w/External PSC) 10
Linked vCenter Servers (w/Embedded PSC) 15

Note: As of vSphere 6.7, you can have up to 15 Embedded VCSA's within an ELM.

The second is the "Maximum PSCs per vSphere Domain" which defines the maximum number of PSC's that can be part of a single SSO Domain, pretty straight forward. The third is the "Maximum PSCs per site behind a load balancer" which just adds an additional constraint when using a load balancer with your PSCs.

Platform Services Controller Maximum

Configuration Maximum
Maximum PSCs per vSphere Domain 10
Maximum PSCs per site behind a load balancer 4

[Read more...]