Re: OT: Performance of VM

I am consultant that specializes in virtualizing oracle enterprise level workloads. I’m picking up Postgres as a secondary skill. You are right if you don’t manage it properly, you can have problems running enterprise workloads on vm s. But it can be done with proper management. And the HA and DR advantages of virtual systems are huge.

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> On Feb 10, 2018, at 5:20 AM, Robert Klemme <shortcutter(at)googlemail(dot)com> wrote:
>
>> On Mon, Feb 5, 2018 at 5:22 PM, Andrew Kerber <andrew(dot)kerber(at)gmail(dot)com> wrote:
>> Have them check the memory and CPU allocation of the hypervisor, make sure
>> its not overallocated. Make sure the partitions for stroage are aligned (see
>> here:
>> https://blogs.vmware.com/vsphere/2011/08/guest-os-partition-alignment.html)
>> . Install tuned, and enable the throughput performance profile. Oracle has a
>> problem with transparent hugepages, postgres may well have the same problem,
>> so consider disabling transparent hugepages. There is no reason why
>> performance on a VM would be worse than performance on a physical server.
>
> Not theoretically. But in practice if you have anything run in a VM
> like in this case you do not know what else is working on that box.
> Analyzing these issues can be really cumbersome and tricky. This is
> why I am generally skeptical of running a resource intensive
> application like a RDBMS in a VM. To get halfway predictable results
> you want at least a minimum of resources (CPU, memory, IO bandwidth)
> reserved for that VM.
>
> Anecdote: we once had a customer run our application in a VM (which is
> supported) and complain about slowness. Eventually we found out that
> they over committed memory - not in sum for all VMs which is common,
> but this single VM had been configured to have more memory than was
> physically available in the machine.
>
> Kind regards
>
> robert
>
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