Abstract: In an erasure-coded cloud storage system, the performance of data updates is often limited by network overhead. To end this, based on Cross-Rack-Aware Update (CAU) data update scheme, we propose an XOR based Tape ARchive Cross-Rack-Aware Updates (TAR-CAU) data update scheme. TAR-CAU is designed in terms of the two design primitives: 1) as the updates are small, we can pack several data blocks of data update into one block to reduce the number of network round trips, and accelerate the data transmission; 2) XOR-based data update scheme is used to accelerate data encoding and decoding. The simulation experiments and local cluster experiments show that, when the data updates are small, TAR-CAU can increase the data update throughput by at least 44% compared with the CAU.