vSAN1

I am attempting to configure vSAN, and successfully reach 'Claim disks'. At that point I had both HDD and Flash drives available on my ESXi systems, but could not successfully claim disks, because I apparently had no cache I could select

I attempted to correct this problem using an option in  host configuration, ‘Virtual Flash Swap Cache Configuration’ however despite configuring virtual cache the vSAN 'Claim disks' menu of my configuration still found no cache for me to use. Additionally, I no longer see the Flash drives coming up as choices as they were before.

Any help or suggestions, would be greatly appreciated.

Hello jediller​

Welcome to Communities!

"I attempted to correct this problem using an option in  host configuration, ‘Virtual Flash Swap Cache Configuration’"

Fairly certain this writes a partition to the device which makes this unusable to vSAN:

'An individual flash device must be exclusively allocated to the virtual flash resource. No other vSphere service, such as vSAN or VMFS, can share the device with the virtual flash resource.':

https://docs.vmware.com/en/VMware-vSphere/6.5/com.vmware.vsphere.storage.doc/GUID-392BFA2C-CC7A-40BC-BC33-4089714E3B81.html

You likely are not seeing devices available to be consumed by vSAN due to existing partitions on the devices (including the one put on a drive by enabling Flash Cache) - vSAN requires blank drives with no partitions.

You can check what partitions are on each device via the Web Client:

Host > Manage/Configure > Storage Devices > Click device > Properties (lower pane) > Primary Partitions

Or via CLI:

# vdq -q

If this is a nested set-up or you are trying to present HDDs as SSDs you may need to mark these as SSD

https://docs.vmware.com/en/VMware-vSphere/6.5/com.vmware.vsphere.storage.doc/GUID-99BB81AC-5342-45E5-BF67-8D43647FAD31.html

Hope this helps and let us know your findings based on the above.

Bob

Thanks Bob,

as vdq -q shows, you are correct [here is one entry that shows that]

   {

      "Name"     : "naa.5000c500a0a36f3f",

      "VSANUUID" : "",

      "State"    : "Ineligible for use by VSAN",

      "Reason"   : "Has partitions",

      "IsSSD"    : "0",

"IsCapacityFlash": "0",

      "IsPDL"    : "0",

   },

After reading your post, I finally figured out how to remove the virtual Flash.

The 2nd portion of my problem was I needed to add cache. I found I could specify the Flash disks as cache,

Mark the non Flash disk as Flash, and then add it has capacity.

This seems like an odd solution to me, but it works.

Hello jediller​,

"I found I could specify the Flash disks as cache,"

One Flash device is required as thec cache-tier of each Disk-Group - whether it needs to be marked as Flash depends on whether this is detected as SSD initially(as per the doc above).

"Mark the non Flash disk as Flash, and then add it has capacity."

You shouldn't have to mark HDDs as SSDs to add them as capacity-tier to disk-groups.

Maybe it won't allow adding HDDs to second or more disk-groups due to the first disk-group being configured like this (and you can't mix All-Flash with Hybrid disk-groups).

In general this shouldn't be done with physical HDDs as they won't work very effectively when treated as though they were HDDs (though if they are nested there may not be much difference) as per the above doc:

"Marking the HDD devices as flash might deteriorate the performance of datastores and services that use them. Mark the devices only if you are certain that they are flash devices."

So if these are physical HDDs I would advise reconfiguring these disk-groups accordingly

Bob