Connecting VSAN hosts to Physical SAN

[jrashtc]

As a preface, I know it is possible to do this. I am just checking if there are risks involved I am unaware of.

Earlier this year I built out a VSAN cluster to replace our old server cluster that was stretched for resources. This old cluster is connected to a Nimble SAN. I still have a couple of the servers running in the old cluster connected to the Nimble SAN because I don't want to burn out the SSDs with constant overwriting of security camera footage, and the SAN is a big chunk of storage that is easy to dedicate to the camera footage.

Are there any risks of also connecting hosts in a VSAN cluster to a separate ISCSI disk? I cant think of anything off the top of my head that I would expect to be a problem, but I figure I'm better off being paranoid and checking rather than finding out the hard way.

[CallistoJag]

We have been doing this in production for literally years in a huge environment with 0 issues 🙂

[BivasM]

There shouldnt be any problems . But i would be careful if you are onboarding SAN that is connected to a different vcenter. Sometimes i have seen issues where vm's get discovered on both vcenters (if they are not connected through ELM). 

[jrashtc]

It is the same vCenter, which has already been moved off of the SAN and to the vSAN.

Good point though to watch out for that in potential other setups I work with in the future.

[jrashtc]

Sounds Good, thanks for helping me shed some anxiety and trepidation.

Out of curiosity, how are you utilizing the physical SAN in your environment? Low priority/performance VMs, Backups, Something similar to my plan of storing security camera footage to save on SSD writes?

[BivasM]

usually we use class based storage.

there are tow groups in physical san, 

1 (RAID 10) WITH SSD --- this datastore is for DB, high transactional apps, io intensive apps

2 (RAID 6) WITH SSD --- 2nd tier critical vms

high performance nas for application logs.

cctv footage is not that important to us . we used to write them on regular sas based raids (local raid)

[TheBobkin]

@jrashtc, the only times I have ever seen non-vSAN external storage attached to vSAN nodes impact anything is where this storage is acting up and this would only impact monitoring aspect (vsanmgmtd) not data access/performance/functionality - the query storage APIs used for some of the Skyline Health checks appear to initially query all attached storage devices (e.g. to check if they have vSAN partitions on them) and only after that perform the health check queries - if there is some storage device that has some issue like it appears present but goes through a long timeout before returning info (even if that is 0B space available because of issues with it), this can cause the initial query storage APIs to timeout possibly resulting in later health queries timing out and this node not reporting correctly to Skyline Health and/or vSAN Performance stats.