MABEs
Contributor
Contributor

Calculate VMware vSAN stretched cluster

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Hi,

How do the usable storage change when I stretch a VSAN cluster? i.e do both site contribute storage? in this case doubling the storage?

Example

Site 1

6 Hosts with a all flash VSAN with 30 tb of usable storage.

Site 2

6 Hosts with a all flash VSAN with 30 tb of usable storage.

If I stretch the vSAN over site 1 and 2 will I get 60 Tb of usable storage?

Thanks

//Marcus

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TheBobkin
VMware Employee
VMware Employee

Hello Marcus,

Welcome to Communities!

If you created one big stretched cluster instead of 2 smaller clusters then yes this would have a 60TB vsanDatastore.

The thing is though, I don't believe that there is any feasible method of merging two clusters directly like this.

What would be the likely method of achieving this would be:

- Start advanced Storage vMotioning VMs from one cluster to the other (assuming shared vCenter).

- Once the destination cluster is starting to approach 70-80% storage capacity used, put a node or two (one at a time) from the cluster that is to be evacuated in Maintenance Mode with 'Full data migration'.

- Once data has been evacuated you can add these hosts to the destination cluster.

- Go back to step one and proceed like this until all the data and hosts are in one big cluster.

- Set-up the Witness Appliance running as a VM on some other infrastructure

- Configure Stretched cluster and Fault Domains for the sites (or as desired).

How much free space you have on each cluster and the transfer speed will determine how long this will likely take.

If one cluster has significantly less storage space used then this would be the one to evacuate.

If you have SAN-storage another method would be to use this as an intermediary as a Storage vMotion destination (and do the same steps as before of evacuating nodes once used capacity decreases).

This or a simple back-up VMs from cluster, restore VMs to destination, delete original VMs.

Bob

-o- If you found this comment useful please click the 'Helpful' button and/or select as 'Answer' if you consider it so, please ask follow-up questions if you have any -o-

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TheBobkin
VMware Employee
VMware Employee

Hello Marcus,

Welcome to Communities!

If you created one big stretched cluster instead of 2 smaller clusters then yes this would have a 60TB vsanDatastore.

The thing is though, I don't believe that there is any feasible method of merging two clusters directly like this.

What would be the likely method of achieving this would be:

- Start advanced Storage vMotioning VMs from one cluster to the other (assuming shared vCenter).

- Once the destination cluster is starting to approach 70-80% storage capacity used, put a node or two (one at a time) from the cluster that is to be evacuated in Maintenance Mode with 'Full data migration'.

- Once data has been evacuated you can add these hosts to the destination cluster.

- Go back to step one and proceed like this until all the data and hosts are in one big cluster.

- Set-up the Witness Appliance running as a VM on some other infrastructure

- Configure Stretched cluster and Fault Domains for the sites (or as desired).

How much free space you have on each cluster and the transfer speed will determine how long this will likely take.

If one cluster has significantly less storage space used then this would be the one to evacuate.

If you have SAN-storage another method would be to use this as an intermediary as a Storage vMotion destination (and do the same steps as before of evacuating nodes once used capacity decreases).

This or a simple back-up VMs from cluster, restore VMs to destination, delete original VMs.

Bob

-o- If you found this comment useful please click the 'Helpful' button and/or select as 'Answer' if you consider it so, please ask follow-up questions if you have any -o-

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MABEs
Contributor
Contributor

Hi Bob,

Thanks for your helpful answer.

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