Hello!
Distributed RAID Expansion is a non-disruptive process that will actively add storage in chunks into the main storage pool (so trickle in capacity) as it re-stripes the data across the added capacity.
Here are the rules for Distributed RAID Expansion:
1. You can expand an existing array (live, no downtime) in increments of 1-12 (any number inclusive).
2. For drive types that allow more than one rebuild area you can add additional spare regions on expansion
3. You cannot change the drive geometry (so a 10+P+Q remains a 10+P+Q on expansion)
4. only 1 expansion can be active for any Array at any given time.
5. You must have spare capacity in order to expand, the more spare capacity you have in the array, the faster the expansion, as with easy tier, the array requires some swing space to perform the data movement.
6. Capacity will trickle in to the pool, you won't get 100% when you run, and the task will run in the background as a lower priority than active IO or rebuild to avoid disrupting the system.
For a really good write up, I recommend Barry and Andy's blog, the specific article is: https://barrywhytestorage.blog/2020/03/25/draid-expansion-the-important-details
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Evelyn Perez
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