Re: PostgreSQL benchmarked on XFS vs ZFS vs btrfs vs ext4

On 14/09/2011 09:30, Toby Corkindale wrote:
> On 14/09/11 12:56, Andy Colson wrote:
>> On 09/13/2011 08:15 PM, Toby Corkindale wrote:
>>> Hi,
>>> Some months ago, I ran some (probably naive) benchmarks looking at how
>>> pgbench performed on an identical system with differing filesystems.
>>> (on Linux).
>>>
> [snip]
>>
>> Did you test unplugging the power cable in the middle of a test to see
>> which would come back up?
>
> Heh, no, but it'd be interesting to see..
>
> I wonder if turning a virtual machine off has the same effect?

No, never the exact same effect.

There are two things to consider: if/when/how the OS flushes the data to
the hardware and if/when/how the hardware flushes the data to physical
storage. You can simulate only the failure of the first part with a
virtual machine, but not the second (unless you bring down the VM host...).