Virtualization was a breakthrough innovation in the world of data centers. Server virtualization introduced a software layer called the hypervisor that abstracted the CPU, storage, and memory of physical servers into pools of virtual resources. Virtual machines (VM) running on the hypervisor hosts ran their own operating systems and shared processor, memory, and storage. Applications could be hosted on multiple VMs residing on fewer physical servers -- enabling significant cost savings from consolidation and portability. Virtualization was appealing at a high level for consolidation, potential cost savings, simplified maintenance, and far more flexibility in backups and DR.
The classic three-tier architecture with Storage Area Networks (SANs) consisted of compute, storage, and networking that were disaggregated but connected. These architectures started gaining prominence due to their dedicated high-speed networks specifically purposed for data storage. SANs were built on Fiber Channel technology (FC) or on Internet Small Computer Systems Interface (iSCSI) with the latter being less expensive. SANs provided improved data security, highly responsive backups, increased scalability, and reliable disaster recovery.
Fairly complex to setup, configure and maintain, the SANs often required a substantial capital outlay and had their own share of problems, such as hardware compatibility, performance, and multivendor support issues. To address these challenges, Converged Infrastructures (CI) solutions were designed with highly integrated configurations.