Currently, HPC storage systems still use hard disk drive (HDD) as their dominant storage device. Solid state drive (SSD) is widely deployed as the bu er to HDDs. Burst bu er has also been proposed to manage the SSD bu ering of bursty write requests. Although burst bu er can improve I/O performance in many cases, we nd that it has some limitations such as requiring large SSD capacity and harmonious overlapping between computation phase and data ushing phase.In this paper, we propose a scheme, called SSDUP+ 1 . SSDUP+ aims to improve the burst bu er by addressing the above limitations. First, in order to reduce the demand for the SSD capacity, we develop a novel method to detect and quantify the data randomness in the write tra c. Further, an adaptive algorithm is proposed to classify the random writes dynamically. By doing so, much less SSD capacity is required to achieve the similar performance as other burst bu er schemes. Next, in order to overcome the di culty of perfectly overlapping the computation phase and the ushing phase, we propose a pipeline mechanism for the SSD bu er, in which data bu ering and ushing are performed in pipeline. In addition, in order to improve the I/O throughput, we adopt a tra c-aware ushing strategy to reduce the I/O interference in HDD. Finally, in order to further improve the performance of bu ering random writes in SSD, SSDUP+ transforms the random writes to sequential writes in SSD by storing the data with a log structure. Further, SSDUP+ uses the AVL tree structure to store the sequence information of the data.We have implemented a prototype of SSDUP+ based on OrangeFS and conducted extensive experiments. e experimental results show that our proposed SSDUP+ can save an average of 50% SSD space, while delivering almost the same performance as other common burst bu er schemes. In addition, SSDUP+ can save about 20% SSD space compared with the previous version of this work, SSDUP, while achieving 20%-30% higher I/O throughput than SSDUP.