One of the applications we were troubleshooting for performance issues was having bottleneck in the block devices. The monitoring we did revealed average service time greater than 150 ms consistently.
Even the architects were surprised to see such bad performance from their favored storage device from EMC.
The solution turned out to be simple, storage device was changed from EMC to XIO and average service times came down to less than 10 ms.
So if you are facing storage issues in your project, you may want to consider XIO storage solutions.
In last few years EMC storage had been bottleneck for several applications we did performance troubleshooting for, most of the times the storage performance was improved by making changes in the storage policy where you get access to the fastest storage media in the EMC rack, things get complicated when multiple applications compete for the fastest storage media, you might have to compromise with your performance and live with it.