ONTAP 9.x release notes explicitly say: "Beginning with ONTAP 9.0, root-data partitioning is supported by the FAS2600 series on hard disk drives (HDDs) in external disk shelves." If what you say is true, I expect release notes to be fixed.
I can confirm that the Sept 2017 9.2 release notes state that ADP on external shelves for the 2600 from 9.0 - interestingly this is not in the 9.0 release notes. I was earlier relying on an internal doc on ADP released July 2017.
Clearly only one is correct - I will find out and update.
Ok - I have clarified the situation with our TME team - Only the FAS2650 supports ADPv1 on an external shelf of NL-SAS drives if and only if the internal slots are empty. Additional shelves added to a system with internal drives are not partitioned.
The NL-SAS drives that we have available are all large form factor (LFF), while the internal shelf on a FAS2650 is small form factor (SFF), and we do not have a FAS2240-4/2554 type of system with controllers in a 24-slot LFF shelf in our most recent generation of hardware, therefore there may be a desire under some situations to deploy one with only "external" drives, and it is of course desirable to have them partitioned for the root aggregates.
The FAS2620 does not have this behavior, as it is a LFF 12-slot enclosure, but we also have SAS and SSD SFF drives in a LFF carrier to fit in it, so the internal slots can be used for the root partition under any of these configs.
There's a non-public bugFeature Request that allows ADP to include external shelves on FAS26xx, starting with ONTAP 9.1.
If you're running ONTAP 9.2, the new Option 9 (ADP) boot menu option is the cat's meow.
Oh! Now it became even more confusing. 😞 Do you refer to the same feature as Alex (ADP on external shelves withoout internal disks) or you mean that it is possible to force ADP on external disks even with internal disks present?
The behavior I am referring to is the automatic partitioning performed when ONTAP 9.x tries booting on a system with only unpartitioned, un-owned drives, which is the equivalent of option 9b in the new sub-menu.
I had to revert from 9.2 to 9.1p8 to be officially supported by VEEAM, and since the systems are new I took the chance to reinit just in case I fouled up the revert (there's no data yet).
Anyway, by default (standard boot menu 4 initialize), with the external shelf attached on my FAS2620 (internal is 12 4tb drives, external is 8 4tb drives and 4 SSDs) ADP did spread accross the spinning disks on both shelves:
redacted1::> version NetApp Release 9.1P8: Wed Aug 30 13:33:41 UTC 2017
An update to my last post. It seems when the FAS2620 did ADP accross our two shelves of NL-SAS, no root-data spares were created. In any case, I think I'm just going to go back to a single internal shelf of ADP, as I lose a little space, but on this system is feels a bit safer.
Entry-level FAS systems (with HDDs) will only perform ADP on the internal/embedded drives.
AFF systems will use ADP on up to 48 SSDs across multiple shelves. However, for AFF-A220/A220, you will typically see ADP on the 24 internal SSDs only because NetApp Mfg. initializes the system without any add-on storage.
12-drive entry-level FAS systems (FAS2520, 2620, 2720) with HDD sizes that require RAID-TEC need to be explicitly set RAID-TEC to "false" for internal drive ADP (i.e. LOADER> setenv bootarg.raid.allow-raid-tec? false) to ensure that ADP will use 3d+2p+1s P1 partitions for each node. Important: Once you have initialized the system, set this bootarg back to true so that any additional large-HDD RG's use TEC for optimal protection.
If the entry-level FAS system does not contain any internal drives, ADP will use external storage.