if SSD datastore is detected as HDD what performance issues can be experienced?

[zenivox]

Hello, maybe a dumb question as it is clear that if a LUN is SSD it should be seen as SSD, and if that is not the case it must be corrected. However... on a customer site it is difficult to justify the actions needed to fix this many other VMs are just working fine... so the question is:

if SSD datastore is detected as HDD what performance issues can be experienced? HDD have seek times which don't exist on SSD, but does anybody know what to look for in the investigation?

[IRIX201110141]

None.

The ESXi needs to now if its a SSD because than it enable configure options like

- specify a Datastore as Cache/Swap Device

- for vSAN is makes the device selectable for a Caching Device

otherwise these options are grey out or showing not device available.

Again.. it have nothing todo with performance.

Regards,
Joerg

[zenivox]

many thanks Joerg!

this KB VMware Knowledge Base  states that to perform the change I need to shutdown the VMs or probably enough to move them out of the datastore. So it is an important change then? I have 6.5 and the KB does not cover that version. Maybe outdated? Unfortunately I don't avail of a test environment

[IRIX201110141 · Accepted solution]

vCenter 6.5 and up have its own button for that task (as vSAN becomes more famous) in the GUI so the KB you posted is indeed only for < 6.5 and needs to be performend on the ESXi commandline level.

If the ESXi is not using the Datastore for something like this

- Scratch Disk

- HA Datastore heartbeating?

you can change the Disk type on the fly. It doesnt matter if VMs are already there and up and running.

If you cant and got an Error.... dont panic..... you have to reboot the host to see the changed effects. Thats it.

Regards,
Joerg

[zenivox]

thanks again