Splunk is a powerful data analytics platform that collects, indexes, and analyzes data from virtually any source, including application and machine-generated data in a searchable repository from which it can generate meaningful insights. Splunk makes this data available and usable to organizations to quickly analyze and gain insights into application problems, security, compliance, and web analytics issues. Splunk works very well for enterprises that are required to store and process large volumes of data when used with a scalable, highly available, cost-effective solution.

EMC solutions provides them for Splunk –

• Isilon delivers a complete scale-out network attached storage system, and together with the EMC Isilon OneFS Operating system combines file systems, volume managers, and data protection into a single unified software layer, creating a single intelligent file system that spans all nodes in an Isilon cluster.
• High availability and scalability is required at the compute level to enable management and growth of any Splunk deployment. VMware vSphere provides the dynamic compute scalability and high availability allowing seamless scale-out and complete management of any Splunk deployment.

For more, read EMC reference Architecture for Splunk