Yellow Bricks

by Duncan Epping

VMware

What if the disk controller driver included in my vendor’s ESXi image is not on the vSAN HCL?

· · 7 Comments

Sometimes unfortunately there are situations where a vendor’s ESXi image includes a disk controller driver that is not on the vSAN HCL/VCG (VMware Compatibility Guide). Typically it is a new version of the driver which is supported for vSphere, but not yet for vSAN. In that situation, what should you do? So far there are two approaches I have seen customers take:

  1. Keep running with the included driver and wait for the driver to be supported and listed on the vSAN HCL/VCG
  2. Downgrade the driver to the version which is listed on the vSAN HCL/VCG

Personally, I feel that option 2 is the correct way to go. The reason is simple, vSphere and vSAN have different certification requirements for disk controllers and the vSAN certification criteria are just more stringent than vSphere’s. Hence, sometimes you see vSAN skipping certain versions of drivers, this usually means a version did not pass the tests. Now, of course, you could keep running the driver and wait for it to appear on the vSAN HCL/VC. If however, you hit a problem, VMware Support will always ask you first to bring the environment to a fully supported state. Personally, I would not want the extra stress while troubleshooting. But that is my experience and preference. Just to be clear, from a VMware stance, there’s only one option, and that is option two, downgrade to the supported version!

Is a crossover cable needed for vSAN 2-Node Direct Connect?

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I had this question last week around vSAN 2-node direct connect and whether using a crossover cable is still required to be used or if a regular CAT6 cable (CAT 5E works as well) can be used. I knew the answer and figured this would be documented somewhere, but it doesn’t appear to be. To be honest, many websites when talking about the need for crossover cables are blatantly wrong. And yes, I also spotted some incorrect recommendations in VMware’s own documentation, so I requested those entries to be updated. Just to be clear, with vSAN 2-Node Direct Connect, or vMotion, or any other service for that matter, you can use a regular CAT6 cable. I can’t recall having seen a NIC in the past 10 years that does not have Auto MDI/MDI-X implemented, even though it was an optional feature in the 1000Base-T standard. In other words, there’s no need to buy a crossover cable, or make one, just use a regular cable.

Can’t have more than 255 characters in VM notes using the vSphere (h5) Client?

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I had a question about a limit a customer was hitting with the VM notes using the vSphere (H5) Client. They noticed that whenever they got around ~260 or so characters, they could not add any characters beyond that unless they deleted some. After talking to an engineer within VMware I found out that this is indeed the limit for the vSphere Client today. Through the API, and of course also PowerCLI, you can go beyond the 255 if needed. Also with the Web Client you could do this. If you are hitting this issue, please be aware that it is a known issue and VMware is looking to resolve it hopefully soon.

VMs which are not stretched in a stretched cluster, which policy to use?

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I’ve seen this question popping up regularly. Which policy setting (“site disaster tolerance” and “failures to tolerate”) should I use when I do not want to stretch my VMs? Well, that is actually pretty straight forward, in my opinion, you really only have two options you should ever use:

  • None – Keep data on preferred (stretched cluster)
  • None – Keep data on non-preferred (stretched cluster)

Yes, there is another option. This option is called “None – Stretched Cluster” and then there’s also “None – Standard Cluster”. Why should you not use these? Well, let’s start with “None – Stretched Cluster”. In the case of “None – Stretched Cluster”, vSAN will per object decide where to place it. As you hopefully know, a VM consists of multiple objects. As you can imagine, this is not optimal from a performance point of view, as you could end up having a VMDK being placed in Site A and a VMDK being placed in Site B. Which means it would read and write from both locations from a storage point of view, while the VM would be sitting in a single location from a compute point of view. It is also not very optimal from an availability stance, as it would mean that when the intersite link is unavailable, some objects of the VM would also become inaccessible. Not a great situation. What would it look like? Well, potentially something like the below diagram!

Then there’s “None – Standard Cluster”, what happens in this case? When you use “None – Standard Cluster” with “RAID-1”, what is going to happen is that the VM is configured with FTT=1 and RAID-1, but in a stretched cluster “FTT” does not exist, and FTT automatically will become PFTT. This means that the VM is going to be mirrored across locations, and you will have SFTT=0, which means no resiliency locally. It is the same as “Dual Site Mirroring”+”No Data Redundancy”!

In summary, if you ask me, “none – standard cluster” and “none – stretched cluster” should not be used in a stretched cluster.

Sharing my vSAN 7.0 U1 webinar, watch it now!

· · 1 Comment

I recorded a webinar a while back. It was streamed last week, and I figured that as I have the recording here, I may as well share it with you. In this webinar I discuss many of the new features which were introduced as part of vSAN 7.0 U1, features like HCI Mesh, IO Insight, enhanced File Service capabilities, and much more. The session is about 40 minutes long, but of course, the great thing about youtube is that you can play it at a different speed. Hope you will enjoy it! Click on the video below, or simply follow this link to youtube. Make sure to like the video, and subscribe to my channel as well!