An architect is designing a new Hybrid five node vSAN cluster for a customer who is planning to use vRealize Automation to provision 600 virtual machines into that cluster, with expected growth up to 1,000 VM. Each VM has a 40GB thick-provisioned disk.
Which flash disk size is required for the cache tier per ESXi node to meet all requirements?
In a vSAN configuration, the cache tier flash disk size is recommended to be 10% of the storage capacity of the node. Given that each VM requires 40GB and that the cluster may grow up to 1000 VMs, the total storage needed is 40,000GB. Divided by 5 nodes, this is 8,000GB per node. Therefore, 10% of 8,000GB is 800GB. However, there is a cap on the maximum cache disk size that is usable in vSAN 7.0, which is 600GB. Hence, despite calculations suggesting an 800GB cache, the correct answer must consider this cap, making 600GB the appropriate choice.
40GB x 1000VMs = 40 000 GB total max expected usage 40 000GB / 5 node cluster = 8000 GB per node cache should be 10% so 800GB SSD is needed. However this question is stupid from real life perspective. one host can run up to 200 VMs - so what with MM, any failure ? Cluster should be sized with 6 ESXi hosts minumim Also cache should be 10% of raw HDD storage - before RAID policies applied. So what RAID 0? What architect is mentioned in this question? I belive learning one :D :D
Doesn't change the answer to this question but in 7.0, the usable Cache disk size is 600GB, increased to 1.6TB in 8.0 https://kb.vmware.com/s/article/89485
C. The Cache disk size is capped at 600GB in 7.0. Even if you use a bigger disk, only 600GB of it will be used. https://kb.vmware.com/s/article/89485
D for sure cache 10% of total node capacity and hence 8000GB = 800GD SSD cache
I would agree, you should aim for 10% caching minimum. However, there is the 600GB maximum to consider. There is an option to go beyond that with v8, at additional overhead (RAM per node). As they expect to grow, I would install 800GB disks with only 600 usable. Once they grow beyond the 600 machines, enable the option to go beyond that and accept the additional overhead.
in vsan 7 you can only use disk with 600gb max size