IOmeter parameters

Hi everybody ! 

I'm trying to use IOmeter to test a new AFF220 metrocluster. 

However, i don't really know which parameters to use to test it... 

How many workers should i use ? 

I don't really know what is Tranfert Request Size, Align I/Os if you have any ideas ? 

I did a try with 4K 100% random on a windows VM with 10 workers. Display results are showing  36K IOPS, however, on the LUN where resides the VM, can't go over 2000 IOPS.. Don't get that ! 

Thanks !