Described herein is a high-availability storage system having hierarchical levels of storage functions. The storage system may comprise one or more hierarchical levels, each hierarchical level comprising physical servers and be assigned to perform a particular set of storage functions. Each physical server may implement one or more VMs configured to perform only the set of storage functions assigned to the hierarchical level on which the VM executes. VMs of a first hierarchical level may be configured to organize the VMs of a second hierarchical level into a redundant array of storage access servers for providing data reliability and high-availability of the storage system. VMs of a first hierarchical level are configured to produce and route sub-requests to the VMs of a second hierarchical level. Failure of a sub-request is detected and remedied by a VM of the first hierarchical level.