Is Inline Data Compaction Orthogonal to Inline Data Deduplication?

[nachin]

Dear all,

I have been very excited about the inline data compaction feature in ONTAP 9. I read Tech ONTAP and TR4476 and learnt that inline deduplication is orthogonal to inline compaction, which means inline deduplication and online compaction can be both enabled, but a block is inline deduplicated is not compacted.

https://www.netapp.com/us/media/tr-4476.pdf (Page 12)

http://community.netapp.com/t5/Tech-OnTap-Articles/A-Look-Inside-NetApp-Inline-Data-Compaction/ta-p/122362 (search for "orthogonal")

Why are this two features so mutually exclusive? Is there any nature or reason of inline dedupliation that prevents a deduplicated block from being compacted?

Any comment would be appriciated.

[asulliva]

Hello @nachin,

If the block is (inline) deduplicated then it's never written to disk...the metadata is simply updated to reference the block that already exists.

Hope that helps.

Andrew