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[Jonas Maebe]

On 07/12/16 09:42, Francois Gouget wrote:
> On a spinning disk 2500+ IO/s only makes sense if they are contiguous.
> 200 IO/s however makes sense for random IO. But eve on vm1 the disk
> image file is not that fragmented. And given that it was restored from
> the same backup on both machines at a couple of days interval I see no
> reason for one to cause random IO and not the other.

I don't know how the snapshot-revert operation works internally, but 
with the slow VM you have a total of 289,844 KB written, while with the 
fast one it is 353,092 KB.

Perhaps with the slow one, it "optimizes" the operation by not writing a 
bunch of unchanged blocks, which in turn requires more seeking. You 
could maybe try strace'ing both to look at the operations at the file 
system level rather than at the block device one.


Jonas