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ONTAP Discussions

FAS luns marked as flash in vsphere + 9.7



ever since I upgraded my cluster to ontap 9.7 (currently 9.7P4), all luns allocated to vmware esxi hosts (all versions) appear as flash disks in vsphere even though the controllers are “regular” FAS with no ssds at all.

anyone familiar with that?






I don't have ONTAP 9.7 in production so can't really verify for you but in VMWare ESXi/vSphere you can mark  a "disk" or "LUN" as "FlASH", indicating that the disk is an SSD (SSD/flash storage backed). However, as I am reading about it more, it says that if you mark Spinning Disk as 'Flash' it can seriously deteriorate datastore performance, so you have to be cautious.


Has anyone (In your team) marked them as 'flash' accidentally ?


While you confirm the ESXi settings from your side, could you give this output:

Please enter the name of the aggregate below that is hosting the 'LUN' on your FAS Box.
::> aggr show -aggregate <aggr_name> -fields storage-type


::>  version
::> system show





No one marked the disk as flash for sure, I allocated the lun.

version is 9.7P4

storage-type is hdd

model is FAS2650

just for comparison I allocated another lun from a different cluster with FAS9000 running ontap 9.6P6 and the drive type is hdd




Truly Very Interesting!!

9.7P4 is just released two days back "29-May-2020", so I wonder how many customers have upgraded to this version. Let's see if someone on this version can verify this for you. It may well be a 'bug' (Internal) ? No harm in raising a ticket with NetApp just to get this clarified.


Curious - If you provision another test LUN to ESXi from 9.7P4, does that also appear as 'SSD' ? Just to rule out any human errors on VMware settings side.


It happens with every version since 9.7, doesn't matter which P.

And yes, all luns are viewed as "Flash" 😕




Yes, the VPD page reporting for block devices changed in ONTAP 9.7 to report as non-rotating (solid state).


When I investigated this for a customer in 2018, I found the performance issues were relevant to local host disks, not array disks.  With ONTAP, the use of memory and caching mask the rotational characteristics of underlying disks, therefore Engineering made this change for all LUNs regardless of the physical disks used.




@konnerth : Thanks for sharing & confirming this information. Much appreciated.  I think it makes sense,  ONTAP is anyway 'write optimized' and along with flash it actually masks the underline disks ' performance (Even though one could argue that there is a 'significant' difference in latency to the 'End Application' when we compare  all_flash SSD vs  cached HDD aggr). 

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