Yellow Bricks

by Duncan Epping

Duncan Epping

vSAN ESA and the minimum number of hosts with RAID-1/5/6

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I had a meeting last week with a customer and a question came up around the minimum number of hosts a cluster requires in order to use. particular RAID configuration for vSAN. I created a table for the customer and a quick paragraph on how this works and figured I would share it here as well.

With vSAN ESA VMware introduced a new feature called “Adaptive RAID-5”. I described this feature in this blog post here. In short, depending on the size of the cluster a RAID-5 configuration will either be a 2+1 scheme or a 4+1 scheme. There’s no longer a 3+1 scheme with vSAN ESA. Of course, there’s still the ability to use RAID-1 and RAID-6 as well, the RAID-1 and RAID-6 schemes remained unchanged.

When it comes to vSAN ESA, below are the number of hosts required for a particular RAID scheme. Do note, that with RAID-5, of the size of the cluster changes (higher of lower) then the scheme may also change as described in the linked article above.

 

Failures To TolerateObject ConfigurationMinimum number of hostsCapacity of VM size
No data redundancyRAID-01100%
1 Failure (Mirroring)RAID-13200%
1 Failure (Erasure Coding)RAID-5, 2+13150%
1 Failure (Erasure Coding)RAID-5, 4+16125%
2 Failures (Erasure Coding)RAID-6, 4+26150%
2 Failures (Mirorring) RAID-15300%
3 Failures (Mirorring)RAID-17400%

Unexplored Territory Episode 065 – Jatin Purohit discussing Oracle Cloud VMware Solution

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For episode 065 of the Unexplored Territory Podcast I invited Jatin Purohit to discuss Oracle Cloud VMware Solution, and what was introduced since we had Richard Garsthagen on as a guest. Jatin went over all the details, and shared some great use cases with us. Make sure to listen to the episode via your favorite podcast app, or the embedded player below. We are now starting to plan for the upcoming episodes, if you want to be a guest and have an interesting story, or solution, to share, then do not hesitate to reach out.

 

Happy Holidays: vSAN 8.0 U1 Book Discounted to less than 5 USD for the ebook!

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Holidays are coming, so we figured it was time to lower the price of the vSAN ESA 8.0 U1 book! Haven’t bought it yet? The paper edition is around $ 19.99 and the ebook is $ 4.99 (or less, depending on where you live).

It’s a lot of great content for a really low price, and as said we made sure the ebook is priced extremely aggressively as we prefer for technical books not to be printed. Pick it up, the price will return to normal (29.99 and 9.99) after the holiday season!

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

Doing network/ISL maintenance in a vSAN stretched cluster configuration!

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I got a question earlier about the maintenance of an ISL in a vSAN Stretched Cluster configuration which had me thinking for a while. The question was what would you do with your workload during maintenance. I guess the easiest of course is to power off all VMs and simply shutdown the cluster, for which vSAN has a UI option, and there’s a KB you can follow. Now, of course, there could also be a situation where the VMs need to remain running. But how does this work when you end up losing the connection between all three locations? Normally this would lead to a situation where all VMs will become “inaccessible” as you will end up losing quorum.

As said, this had me thinking, you could take advantage of the “vSAN Witness Resiliency” mechanism which was introduced in vSAN 7.0 U3. How would this work?

Well, it is actually pretty straight forward, if all hosts of 1 site are in maintenance mode, failed, or powered off, the votes of the witness object for each VM/Object will be recalculated within 3 minutes. When this recalculation has completed the witness can go down without having any impact on the VM. We introduced this capability to increase resiliency in a double-failure scenario, but we can (ab)use this functionality also during maintenance. Of course I had to test this, so the first step I took was placing all hosts in 1 location into maintenance mode (no data evac). This resulted in all my VMs being vMotioned to the other site.

Now next I checked with RVC if my votes were recalculated or not. As stated, depending on the number of VMs this can take around 3 minutes in total, but usually will probably be quicker. After the recalculation had been completed I powered off the Witness, and this was the result as shown below, all VMs were still running.

Of course, I had to double check on the commandline using RVC (you can use the command “vsan.vm_object_info” to check a particular object for instance) to ensure that indeed the components of those VMs were still “ACTIVE” instead of “ABSENT”, and there you go!

Now when maintenance has been completed, you simply do the reverse, you power on the witness, and then you power on the hosts in the other location. After the “resync” has been completed the VMs will be rebalanced again by DRS. Note, DRS rebalancing (or should rules being applied) will only happen when the resync of the VM has been completed.

Call to action: Help cancer patients enjoy life when still possible!

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CALL TO ACTION: Everyone knows someone with cancer, who passed away as a result of cancer, or maybe even won the battle against cancer. I have seen too many family members and friends fight the battle and lose. For this reason, I decided to participate in the Roparun this year. The Roparun non-profit organization aims to help organizations (financially) in Holland that provide Palliative care for cancer patients.

I will join Team 243 to run from Paris to Rotterdam in a relay fashion next year (May 2024). We will be running with two groups of four people, each group will run in a relay fashion for 4 hours and will then have a 4 hour break, each runner will do 2 kilometers per repetition until the 4 hours has passed. This means it will take roughly 3 days to get back from Paris to Rotterdam. It is my goal to collect as many donations as possible to help cancer patients enjoy life when still possible, every contribution, small or large, is appreciated. I know I have helped many people over the years through my blogs, product feedback, videos, demos, books, and podcasts and many folks have asked if they could return the favor in the past. This is your chance to do so. Again, small or large, it does not matter, all help is appreciated!

All proceeds will go to charity! Please share, repost, and donate, all help is appreciated!
Folks from the Netherlands Holland please use: https://www.roparun.nl/fundraisers/duncan-epping
Folks outside of the Netherlands please use: https://www.gofundme.com/f/living-life-despite-cancer