New AFF-A220 root vol and aggr questions

[RickB]

I have read a the Netapp documentation and searched many forums for answers to the following questions. I just want to confirm the answers or know if anyone has succeeded in 'getting around' what is r
ecommended. All of the questions are in relation to the root volumes for our Netapp AFF-A220, 42 ssd disks (894GB), Ontap 9.7. I am looking to maximize available disk space but do not want to potentia
lly cripple our device by 'cutting corners'.

-It is my understanding that each node requires it's own root volume in order to function properly as that is where the OS for the node is. Just confirming this is the case.

-By default, our device came with each node having a 10 disk root vol raid-dp aggr. This seemed like a huge waste of space so I moved the root vols for each of our nodes to 3 disk aggrs. Is there a pr
oblem with me doing this? Also, the old root vol documentation allowed for a 2 disk RAID4 aggr. Is this still a viable solution in Ontap 9?

-Netapp does not recommend combining data with root vol aggr. I have seen that the issue is that fixing this aggr will result in downtime and inaccessible data. How likely is there to be a problem tha
t would trigger such an event? Is it worth the risk to maximize available disk space?

[SpindleNinja]

-It is my understanding that each node requires it's own root volume in order to function properly as that is where the OS for the node is. Just confirming this is the case.

YES 

-By default, our device came with each node having a 10 disk root vol raid-dp aggr. This seemed like a huge waste of space so I moved the root vols for each of our nodes to 3 disk aggrs. Is there a problem with me doing this? Also, the old root vol documentation allowed for a 2 disk RAID4 aggr. Is this still a viable solution in Ontap 9?

You will want to keep this array using ADP (Advanced Disk Partitioning)  https://docs.netapp.com/ontap-9/topic/com.netapp.doc.dot-cm-concepts/GUID-B745CFA8-2C4C-47F1-A984-B95D3EBCAAB4.html

There's a min required size for the root aggr too - Can be found in hwu.netapp.com   You can also see how the ADP sizing layout is for the root and data/data for the A220 partitions. 

-Netapp does not recommend combining data with root vol aggr. I have seen that the issue is that fixing this aggr will result in downtime and inaccessible data. How likely is there to be a problem that would trigger such an event? Is it worth the risk to maximize available disk space?

This is probably from an old KB,  you cannot put data on the root aggr anymore.  

https://docs.netapp.com/ontap-9/topic/com.netapp.doc.dot-cm-vsmg/GUID-A60F4F83-0034-4DB8-838B-06E9D4BEF9A4.html

[CHRISMAKI]

You're likely looking at partitioned drives, so those 10 devices are slices of larger devices. ADP is the most efficient way to carve up your SSDs.