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I have a FreeNAS file server that uses ZFS for redundant storage. I'm considering running this as a virtual machine using VMWare Workstation (I would give the VM access to the physical disks, rather than using virtual disks).

What problems might I come across, and is this a terrible idea?

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    [irony]For the provided information and specification it is a bad idea.[/irony] – mailq Aug 24 '11 at 21:55
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Performance would be my main concern; even if you're going to give the VM "direct" access to the physical disks, there's still VM-related overhead, and if you've got any decent load you'll have problems earlier in a VM than you would on a physical machine. But benchmark it, it might work OK for your workload.

(For the record, I'd definitely lean towards "bad idea", although I reserve "terrible" for things much, much worse than this).

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  • The demand on the file server is quite limited, so unless performance was abysmal, that's not a big problem. What about potential for data corruption? – Robert Aug 24 '11 at 22:34
  • probably no higher than running it on dedicated hardware really – anthonysomerset Aug 24 '11 at 22:54
  • Not zero, but not appreciably greater than the chances of breaking something on a physical machine. – womble Aug 24 '11 at 22:54
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You really very much do not want to do this, unless you can verify that your virtualisation platform doesn't lie to your guest OS about what it's actually written to the underlying physical disks.

Case in point:
(deleted link to defunct forum) User permanently lost 10TB of data this way.

Virtualbox with its default settings, for example, does lie about this.

Here is another thread on the same issue, and here is the section of the documentation which explains how to change the setting to tell it not to lie about commits.

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  • Your references are all about VirtualBox, yet the question quite clearly talks about VMWare Workstation. – John Gardeniers Oct 11 '11 at 21:26
  • Granted, my references are all about VirtualBox, but the point stands - "unless you can verify that your virtualisation platform doesn't lie to your guest OS about what's actually written to the underlying physical disks" - it would be prudent to check this for VMware, no? – tomfanning Oct 12 '11 at 13:53

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