hiluvatar
Contributor
Contributor

What happens when a local site does not respect SFTT anymore ?

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Hi guys,

I have a question on the streched cluster topic: What happens when a local site does not respect SFTT anymore due to multiple disk/server loss? Let's say my SFTT=1 and lose 2 servers at the same time (or two disks).
A/ The entire site is marked as failed and all VM are restarted on the remaining site
B/ Only affected components are marked as failed and the cluster use remote resources to restart VM (or rebuild data)

The documentation is not clear on the topic.

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depping
Leadership
Leadership

vSAN never sees a site as fully failed unless ALL hosts in a site has failed. The explanation above is a better explanation, I have requested the documentation to be updated as it is fairly complex to read.

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TheBobkin
VMware Employee
VMware Employee

Hello hiluvatar​,

Welcome to Communities.

If you have SFTT=1 on a stretched cluster then either site can withstand losing a component locally and then this site is technically FTT=0 until it gets access to the data again or rebuilds it.

If you lose 2 components in one site then some Objects will become inaccessible from the data on this site, but provided the other site is still FTT=1 (or even FTT=0) the Objects will be accessible from the data there. If the data is still accessible, restarting VMs shouldn't be necessary.

Bob

hiluvatar
Contributor
Contributor

Hello,

thanks for your answer.

This is where I don't understand the documentation :

pastedImage_0.png

Source : https://storagehub.vmware.com/export_to_pdf/vsan-stretched-cluster-2-node-guide

+ in the same document it's said : "If a site has more failures than the local protection policy will allow, then the site is considered failed."

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hiluvatar
Contributor
Contributor

Hello guys,

do you have an update on the topic?

Thanks for your clarification.

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depping
Leadership
Leadership

vSAN never sees a site as fully failed unless ALL hosts in a site has failed. The explanation above is a better explanation, I have requested the documentation to be updated as it is fairly complex to read.

hiluvatar
Contributor
Contributor

Ok thanks a lot Duncan, that's what I thought.

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