Thin VMDK's Not Supported on FC Datastores!?!?

I know, this one caught me totally by surprise as well, but it’s true. We don’t actually use this switch when creating vmdk’s, but after seeing some _shocking_ statistics from our environment, whereby most VM’s with additional vmdk’s were using under 10% of their provisioned space, I decided to look into it.

Now I certainly don’t claim to know everything, so for non-obvious stuff like this I usually look into is as much as I can, then fire off a query to my VMware account team (well… just to the 2 engineers on our account) to see if there’s anything I have missed that would stop me from giving the OK to use it in our environment. Boy, good job I do this (and good job I have some very good SE’s)- the answer I got back isn’t covered in _any_ of the existing documentation.

The official word from VMware is that thin vmdk’s (ie those created with vmkfstools -d thin) are currently not supported for production use on FC datastores. Again, since it’s not possible to create these through the UI I imagine that there aren’t too many people out there affected by this. Even though we aren’t affected, and I can understand why VMware would take such a stance, I’m a bit miffed that there is no mention of this in any documentation I can find. I’m sure that will be changing shortly!

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3 Responses to “Thin VMDK's Not Supported on FC Datastores!?!?”

  1. Dingo Says:

    lmao.. so so funny.. good catch mate

  2. hmm Says:

    Thats’ pretty weird that Thin vmdk is not supported on fc san, i always tought that snapshots where thin vmdk’s? If not, what is the difference between a snapshot and a thin vmdk that makes in unsupported on fc san?

  3. stu Says:

    @hmm not exactly, but from what I understand the primary reason for this situation actually does apply to snapshots as well, in that it’s to do with lack of reporting / alerting in VC. For example there’s no way to set alarms on snapshot growth or age in VI3, getting aggregate snapshot disk usage reports requires custom scripting, and it would be even more complicated to determine when a LUN didn’t have enough free space to cater for the event of all snapshots on the LUN being committed at once! I believe there is a _lot_ more storage reporting coming in VI4, if only VMware could talk about it…

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