Enhancing robustness of an iSCSI-based file system in wireless networks

iSCSI (Internet SCSI) protocols are widely accepted in mobile devices to provide a network-wide extensible storage subsystem. However, the performance of wireless networks is sensitive to environmental factors such as distance and signal interference. This makes file system unstable in a mobile device adopting iSCSI as its underlying storage protocol for a file system. In this paper, we propose two techniques to make an iSCSI-based file system robust in wireless networks. The first one is an adaptive control of iSCSI protocol. This method is to change the timeout parameter of each SCSI request adaptively to current wireless network performance. With this technique, an iSCSI session could be more reliably maintained in the unstable network status. The second one is to create an external journal for a file system - storing journals in a separate block device from the file system. Experiments are conducted in an iSCSI-based ext3 file system in Linux under the WiNET protocol of ultra wide band (UWB) wireless networks. We have shown that the proposed techniques not only guarantee the consistency of the file system without any data loss, but also eliminate the overhead of device re-initialization and the corresponding file system remount.