High performance, high bandwidth, and scalable network storage system is the requirement tendency of most data-intensive applications. Distributed RAID, as a storage architecture, is widely used in cluster and distributed computing environments. But the data placement is mechanical and penalty for maintaining consistency is suffered. In this paper we propose a novel block-level storage architecture called iVISA (iSCSI based Virtual Interface Storage Architecture) which employs the concepts both distributed RAID and virtualization storage. All storage resources distribute in a high performance VI network and are managed by a metadata server. A number of iSCSI target nodes act as the entrances of iVISA system for accessing through iSCSI connections. The storage resources are dynamically allocated to users during I/O accessing. The users? logical block addresses are intelligently and flexibly mapped to the physical block addresses based on the current workload of storage nodes and data layout. The evaluation result shows that better performance can be achieved by allocation and mapping dynamically and flexibly with optimized allocation strategy. A hybrid strategy considering both data layout and load of storage nodes has a 30% higher I/O performance than conventional distributed RAID.