This paper presents the 'HBaseSI' client library, which provides global strong snapshot isolation (SI) for multi-row distributed transactions in HBase. This is the first strong SI mechanism developed for HBase. HBaseSI uses novel methods in handling distributed transactional management autonomously by individual clients. These methods greatly simplify the design of HBaseSI and can be generalized to other column-oriented stores with similar architecture as HBase. As a result of the simplicity in design, HBaseSI adds low overhead to HBase performance and directly inherits many desirable properties of HBase. HBaseSI is non-intrusive to existing HBase installations and user data, and is designed to be scalable across a large cloud in terms of data size and distribution.