I recently posted a deep-dive on root disk-slicing on NetApp Clustered DataONTAP 8.3. And I've had some feedback, both from other partners and colleagues and also from customers. So I thought I would ask the populous en masse. 

It's fair to say that NetApp's Clustered DataONTAP 8.3 is one of the biggest software releases in NetApp's lengthy history. So I want to spend some more time on one of its most key features: Advanced Drive Partitioning, or ADP. 

ADP is the ability to virtually "slice" or in Cisco's terms "abstract" the physical disk blocks in order to make them malleable in ways otherwise impossible without it. And there are two major implementation of this abstraction: root disk slices and FlashPool disk slices. Here, I just want to focus on root disk slices.

With root disk slices, each partition is treated as a distinct virtual disk, and can have it's own RAID level, parity disks, and spare partitions. (Thanks to NetApp SEs and TMEs for providing some of these diagrams)

Now, root disk slices are available only on certain configurations:

1. Entry-level FAS platforms (2500, 2200 series)
2. All-Flash FAS (AFF) platforms (8000, 6000, 3000 series)

While that might seem limiting (notice there is no support for hybrid platforms outside of entry-level systems), it is really based on the 90% use-case methodology. Ninety percent of the time customers who purchase 3000 series, 6000 series, or 8000 series FAS controllers are purchasing multiple shelves and have the room for dedicated root aggregates. And 90% of the time customers who purchase entry-level or AFF systems don't.  

The preceding is a few examples of valid configurations. There are actually a good number of different configurations that can be custom ordered; here's a full list of supported configurations for ADP root disk slices:

Platforms

Disk Shelf Configurations

The root partition size is fixed and automatically set per controller. The actual amount will vary for the total of the root data partition between 430.9GiB (462.7GB) to 431.5GiB (463.3GB). The reason for this 0.13% fluctuation is due to the differing numbers of 4k blocks available with different spindle counts. Of course, the OCD in me wishes it was always just 450GB for a nice round number!

The way that root partition is parceled out is then based upon the number of disk drives with root partitions, calculating for the appropriate RAID level and hot spares as well. Here are the common disk configurations and their corresponding root disk sizes:

Let's look at three real-life examples just to solidify how ADP root disk slices are configured.