vSAN Witness Appliance vs normal ESXi server?

[Benoire]

Hi

This is going to seem like a slightly odd question and appreciate that this sits in the realm of complete nuts; luckily this is just a test lab setup 🙂

I've got a 2 node direct connect vSAN lab setup with the Witness Appliance on a spare ESXi host.  I'm curious to understand if I can do some consolidation for the witness and wondered what the difference was between the vSAN witness appliance vs a normal ESXi install?  Is the appliance setup to do something different (i.e. matched MACs across the NICs, presetup HDD/SSD sizes based on number of VMs) than setting this up in ESXi 6.5 with the same settings manually?

As mentioned, I'm more curious about this as a concept than implementing it at an operational level.

Thanks,

Chris

[peetz]

Hi Chris,

what kind of "consolidation" are you thinking of regarding the Witness appliance?

Indeed it is a normal ESXi install and is treated like this in terms of management, patching etc.

On the other hand it serves a special purpose and that is storing vSAN witness objects only. So it does not run any VMs.

The installation of the appliance could be stripped down, you could e.g. remove a lot of hardware drivers and the embedded VMware Tools ISOs, but that would not really save you anything except some marginal disk space.

- Andreas

[Benoire]

Hey Andreas, appreciate the reply.

This is for a lab test as I'm wondering whether you can host the nested ESXi host in a different hypervisor; completely unsupported and no where near production of course... more playing with a concept. Essentially the lab is running a synology NAS unit and two hosts; I clearly cannot use vSAN without a host witness and the current appliance setup won't install as its an ovf file.  I've got enough memory to dedicate to the ESXi host in the synology VM but I am curious if there is anything extra that is required to make the esxi host act as a witness server if its not an appliance.

I've seen esxi 6.5 installed on MS hyper-v and running fine so wondered whether this was possible in other virtual machine hosts.

Cheers

Chris

[peetz]

Hi Chris,

my understanding is that you can also use a physical ESXi host as a vSAN witness host. You just add and configure it as a witness host when configuring a two host cluster in the Web Client.

I found this related thread where this was done: 2-node vsan stretched cluster with physical ESXi Witness host issues

So you do not necessarily need to use the OVF file for creating a witness host, a regular ESXi install using the ESXi ISO will also work. However, the host needs to have an SSD and at least one hard disk attached which is a technical requirement to qualify as a vSAN cluster member. Luckily this is not a real issue, because in ESXi you can turn any hard disk into a "fake SSD" as described in VMware Knowledge Base .

That will be a fun experiment, let me know how it turns out 🙂

- Andreas

[Benoire]

Hi Andreas

So I got ESXi to install fine, however the issues come about when trying to setup the flash and HDD drives for the witness function; the Synology VMM only allows a free selection of 2 ide drives as it has pre-defined the other 2 as CD-Roms; As it uses qemu and stores disk files, configs in all sorts of random places using GUIDs its hard to track where everything is!  Above the 2 drives, the additional set must be virtIO enabled drives.

Have you ever seen a vib for virtio that could be added to the ISO before installation?  Otherwise, I need to find the ways Synology VMM maps drives to VMs etc. to edit the config files to remove a cdrom and replace it with the third IDE disk...

The hunt continues!  Appreciate the pointers!

Chris