Hello Scryden,
"The servers are in the HCL compatability list and support version 6.5"
Okay, so the servers may be able to run 6.5 but the important part is that the trifecta are supported for vSAN: I/O Controller, Cache SSDs, Capacity SSDs/HDDs.
In comparison to other products (VMware or otherwise), vSAN is QUITE specific about what will work or not, if it is not on the vSAN HCL it is likely for a good enough reason and I can testify that I have seen the potentially gruesome outcome of using unsupported hardware (YMMV, I am sure some things work for some, but maybe just up until they don't...)
http://www.vmware.com/resources/compatibility/search.php?deviceCategory=vsan
(annoyingly this link goes to the ready-node page, you have to click 'Build Your Own based on Certified Components' then select one of the trifecta and specify as needed)
"Why is RAID1 not supported for vSAN?"
Because in a typical scenario you are passing the management of this configuration onto vSAN e.g. vSAN Default Storage Policy has FTT=1 which is essentially R1 but handled at the Object-storage level as opposed to the controller/disk level.
"My biggest concern with RAID0 is that whenever a drive fails, the entire RAID0 set fails. We will then have to replace the failed disk, recreate the RAID0 set and re-add it to the vSAN cluster. I'd rather have RAID1 disks which I can hot swappable replace whenever a disk fails."
This is where Storage Policies come in - you can specify on a per-Object basis (vmdk/namespace/.vswp/snapshot) whether you want it as FTT=0 (single copy of data) or FTT=1 (Essentially R1 + a tie-breaker component) and then multiple other configurations such as stripe-width, space-reservations, cache-reservations, IO limits etc.
If you run FTT=1 (as most seem to do) If a single copy of this R1 becomes unavailable the VM keeps running and the missing mirror is rebuilt if its absence is not transient (e.g. a host going down for a short time).
If a disk fails in a vSAN host (with R0 not pass-through), you can hot-replace it if your controller supports hot-swap, if not, it is not a huge deal as if you are running ROBO with all VMs FTT=1 you can run all VMs off one node, shut down the affected node replace the failed disk and bring it back up.
This reference is going back a long time but the architecture-design remains the same and might help elaborate on this more:
Storage Controller RAID0 mode
For storage controller RAID adapters that do not support pass-through mode, Virtual SAN fully supports RAID0 mode. RAID0 mode is utilized by creating a single drive RAID0 set via the storage controller software, and then presenting this to Virtual SAN. You will then have to mark which of these single drive RAID0 sets are SSDs within vSphere. When RAID0 mode is utilized, the the following occurs
Virtual SAN will not manage hot-plug capabilities of drives
Hot-plug will be managed by the storage controller software
Another consideration since you are thinking of going ROBO:
Do you have another site/cluster somewhere relatively near that you can run the Witness and/or vCenter from?
If you feel that I did not answer anything completely feel free to PM me or ask more questions here.
Bob
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