TESA: a Temporal and Spatial Information Aware Writeback Policy for Home Network-Attached Storage Devices

Home Network-Attached Storage (NAS) provides an easy way for data sharing and backup among multiple consumer electronic devices in home networks. Because of large capacity and cost effectiveness, disks are widely adopted in home NAS devices. In addition, data writes are common for many home NAS devices since these devices are usually used for data storage and backup. A writeback policy selects which dirty buffers are to be flushed to the disk, which is critical to the system performance under write-intensive workloads. In this paper, an intelligent writeback policy for home NAS called TESA is proposed. In contrast to most existing writeback policies, TESA considers both temporal and spatial information of the dirty buffers to improve the writeback performance. Considering the temporal information helps to reduce the frequency of writing back recently used dirty buffers, and hence leads to reduced write traffic. Considering the spatial information causes a reduction in the overall seek time and rotation delay of the dirty buffer writeback. The TESA writeback policy was implemented on a NAS evaluation board running Linux kernel. The performance results shows that TESA yields a significant performance improvement (i.e., up to 33.1%) over the original writeback policy of Linux. Moreover, TESA outperforms the policy that considers only the temporal information of the dirty buffers by up to 21.0%, and it also has up to 10.9% performance improvement over a previous policy that considers both the temporal and spatial information(1).