Storage Utilization

  • 7 November 2018
  • 2 replies

Userlevel 1
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I have turned on Windows Dedup for some of my file servers that reside on AHV, however the storage reduction is not reflected on Prism. Any thoughts as to why?

I wish I could run the Capacity Dedup from AHV however the last time that I turned it on I received the following alert:

Do not replicate protection domain XXXXXXX comprising entities from the storage container that have deduplication enabled to a single node remote site XXXXXXX. (XXX denote omitted field)

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2 replies

Userlevel 1
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i think Windows does not directly wipe the deleted files "either from dedupe or other deletion" so the storage layer will always see used blocks of these deleted files.
i do not know about AHV, but i think you have to zero-fill the deleted blocks using sdelete or other tools to let the storage layer know these blocks are not used anymore so it can reclaim its used space.
Userlevel 3
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So Nutanix will leverage capacity dedupe on new writes, not existing extents. One trick is to use a tool called vdisk manipulater for fingerprinting existing data. This will make the storage think it's a new write and will dedupe it. I'd recommend talking to support. They will gladly assist.

This link talks about the fingerprinting process.

Another alternative is to create a new container with capacity dedupe and migrate the VM to the new container. Keeping your overall capacity in mind. Both will generate additional I/O I've done both and it helps.