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I have a small, two-node setup, plus the virtual VSAN witness virtual appliance. The two physical nodes are directly connected, using two 10GbE nics. Each node has two disk groups containing:

Disk Group 01 (All Flash)

  • 1x 128GB SSD (Cache)
  • 1x 1024GB SSD (Capacity)

Disk Group 02 (Hybrid)

  • 1x 500GB NVMe (Cache)
  • 1x 8TB SATA (Capacity)

Initially, I set up Disk Group 1, naming the datastore "AllFlash". Today, I have added Disk Group 02 and was surprised to discover disk group 02 is added to the same datastore.

I was planning on having a "Gold-Storage" datastore using the All Flash group, and a second "Silver-Storage" datastore containing the Hybrid disk group. It appears this is not possible.

My understanding is that one tags a datastore and then applies that tag to a storage policy (under rules) and finally tags the VM (disk) with the storage policy, thus making the VM migrate its storage to the correct datastore.

I cannot see any way to differentiate which disk group a VM will reside. Is it even possible or am I barking up the wrong tree?

I'm wondering if I should use a "common rule" in the policy, under "Storage I/O Control" and assume VSAN will work it out, based on the IOPS the machine is using, however, I can only seem to add one "Storage I/O Control".

TIA

(ESXi 6.5, VSAN 5.0)

Mario Lenz
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woter324
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  • I don't have an answer as I don't use VSAN but if you google 'Cormac Hogan' - he's a real expert on VSAN who works for VMW - that said I'm a little confused by your 128GB cache?? – Chopper3 Dec 17 '17 at 12:51

1 Answers1

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Disk groups in VSAN contribute capacity to the one VSAN datastore. It's up to VSAN to decide where to store data, not yours. And generally it shouldn't matter to you what disk group a VM resides on.

The only possible use case I can think of is to have, as you do, a "gold" all-flash and a "silver" hybrid disk group. I don't think this is a good idea because at the moment mixing disk group types (all-flash and hybrid) is not supported.

Mario Lenz
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