Krenztor
Enthusiast
Enthusiast

vSAN Design and Sizing Guide 6.5 miscalculation?

I'm going through the VMware vSAN Design and Sizing Guide 6.5 trying to get a better grasp on vSAN.  Going through "14.2 Capacity Sizing Example II" I want to verify that the calculations done for "option 3 All Flash" are correct.  After calculating the Snapshot Storage Consumption the following calculation for Raw Storage Requirements (VMs + Snapshots) is listed as 49.87 TB + 2.5 TB.  The 49.87 TB is pulled from the cache size calculation which in previous examples was only used to get the Snapshot size.  I think that in place of 49.87 TB it is supposed to use 66.5 TB from the Raw Storage Requirements calculation.

I am very new to vSAN so I can't say for sure that this is a miscalculation but I can't find any instructions in the document that would explain why All Flash is calculated differently on these lines compared to Hybrid.  I'd appreciate it if someone with more experience with vSAN could let me know what is correct.  Thanks!

Also worth noting is that the lines "Raw Formatting Storage Capacity = 261.6/0.7" and "Raw Unformatted Storage Capacity = 373/0.99" are copy and pasted from a previous example and not applicable to the calculation for All Flash.

https://storagehub.vmware.com/export_to_pdf/vmware-r-virtual-san-tm-design-and-sizing-guide

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3 Replies
mhampto
VMware Employee
VMware Employee

Hi,

From a detailed read through of the example, I agree it is not explained that clearly. I think the impact of dedupe and compression in the example is not clearly labelled. Looks to be correct from reading through the examples though.

Some great info on the use of vSAN DGs + All Flash here: Designing vSAN Disk groups - All Flash Cache Ratio Update - Virtual Blocks

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dongjh
Contributor
Contributor

Not sure why the size of the Cache SSD should be 400GB, not 4.98TB/20=250GB.

Can somebody explain it ?

Please also see Regarding 'VMware vSAN Design and Sizing Guide'

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dongjh
Contributor
Contributor

????????

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