pros and cons with multiple vSAN disk group

[suhag79]

Hi All,

I have a storage requirement of 15 TB usable disk space. I am looking at the 1.2 TB 10K RPM disk for capacity tier. If i go with default 4 node and 4 disk group then, capacity tier storage requirement will not be suffice. In this case, other option is to go with two disk group per node. But wanted to know, how it will impact on vSAN operation and what are the pros and cons from management and performance point of view. For exa, if whole server goes down then both the DG will go down, in this case, how it will impact the vSAN availability.

Thanks and Regards,

[TheBobkin]

Hello suhag79​,

"But wanted to know, how it will impact on vSAN operation and what are the pros and cons from management and performance point of view.

You will likely get better performance from having multiple disk-groups per host over single disk-group per host as this will have more cache-tier devices to spread the load and may allow better % cache to capacity ratios.

The only downside I can think of is that each new disk-group requires a cache-tier SSD that will require a slot but not provide any capacity.

"if whole server goes down then both the DG will go down, in this case, how it will impact the vSAN availability."

Yes, of course both would be unavailable, similarly if they are both attached to one controller and this fails/crashes both would be unavailable - this will affect availability in the same way as losing a node with a single disk-group would, if you have FTT=1 and the rest of the cluster is okay then the Objects should remain accessible and functional.

Bob

[suhag79]

Thanks TheBobkin

So i need to make sure that, controller (Cisco 12G SAS Modular Raid Controller) which i am going to use support (2 ESXi boot in RAID 1 + 2 SSD + 8 HDD) disks. Right ?

[TheBobkin]

Hello suhag79,

Generally the limitation is not the number of disks the controller can support but the number of slots available in the physical chassis.

As I recall I mentioned previously, avoid putting non-vSAN devices on the same controller as the vSAN devices and if you do this ONLY use them for boot/logging/coredump:

https://kb.vmware.com/s/article/2129050

Bob