Is it possible to Increase storage performance in azure vm using disk striping?
I'm going to preface my answer by indicating I tried this out a few years ago during a demo of Azure's initial IaaS offerings so things have almost certainly changed. 

Yes, you can provision multiple disks and create a spanned volume but I'd also check the segment size of the LUNs. If you're looking for high throughput to scan in tables like for building OLAP cubes on entire fact tables, be sure to indicate a high segment size like 256K. My first IaaS test was with the default 64k segment size better used with OLTP workloads and performance was negatively impacted as a result.