Distributed Storage on Networks of Linux PCs using the iSCSI Protocol

A. BIANCO, J. M. FINOCHIETTO, M. MODESTI, F. NERI,

Shangai, China

Workshop; IEEE International Conference on High Performance Switching and Routing (HPSR); 2008

IEEE

iSCSI is a protocol standardized by IETF that runs on a TCP/IP network to transfer standard SCSI commands. In this paper, we evaluate the performance of iSCSI using standard PCs running a software implementation of the protocol, with the aim of assessing the performance of low-cost distributed storage solutions. First, we compare the performance when using a local disk with those of a virtualized disk connected through a standard Gigabit Ethernet LAN during file I/O operations. Then, we emulate the characteristics of a WAN/MAN setup by using a software emulator within the Linux kernel to generate delays and packet losses, and evaluate the ability of iSCSI to offer Disaster Recovery solutions over high-speed long-distance links. We found that, even if TCP can be tuned to support links with large bandwidth-delay products, iSCSI does not reach good performance due to its windowing scheme that is not large enough, in the used software implementation, to support longdistance links. Finally, we test the iSCSI behavior when other types of traffic share network links with the iSCSI protocol.