As you probably know there is a trend in enterprise computing towards networked storage. This is illustrated by the emergence during the past few years of standards like SRP (SCSI RDMA Protocol), iSCSI (Internet SCSI) and iSER (iSCSI Extensions for RDMA). Two different pieces of software are necessary to make networked storage possible: initiator software and target software. As far as I know there exist three different SCSI target implementations for Linux: - The iSCSI Enterprise Target Daemon (IETD, http://iscsitarget.sourceforge.net/); - The Linux SCSI Target Framework (STGT, http://stgt.berlios.de/); - The Generic SCSI Target Middle Level for Linux project (SCST, http://scst.sourceforge.net/). Since I was wondering which SCSI target software would be best suited for an InfiniBand network, I started evaluating the STGT and SCST SCSI target implementations. Apparently the performance difference between STGT and SCST is small on 100 Mbit/s and 1 Gbit/s Ethernet networks, but the SCST target software outperforms the STGT software on an InfiniBand network. See also the following thread for the details: http://sourceforge.net/mailarchive/forum.php?thread_name=e2e108260801170127w2937b2afg9bef324efa945e43%40mail.gmail.com&forum_name=scst-devel. About the design of the SCST software: while one of the goals of the STGT project was to keep the in-kernel code minimal, the SCST project implements the whole SCSI target in kernel space. SCST is implemented as a set of new kernel modules, only minimal changes to the existing kernel are necessary before the SCST kernel modules can be used. This is the same approach that will be followed in the very near future in the OpenSolaris kernel (see also http://opensolaris.org/os/project/comstar/). More information about the design of SCST can be found here: http://scst.sourceforge.net/doc/scst_pg.html. My impression is that both the STGT and SCST projects are well designed, well maintained and have a considerable user base. According to the SCST maintainer (Vladislav Bolkhovitin), SCST is superior to STGT with respect to features, performance, maturity, stability, and number of existing target drivers. Unfortunately the SCST kernel code lives outside the kernel tree, which makes SCST harder to use than STGT. As an SCST user, I would like to see the SCST kernel code integrated in the mainstream kernel because of its excellent performance on an InfiniBand network. Since the SCST project comprises about 14 KLOC, reviewing the SCST code will take considerable time. Who will do this reviewing work ? And with regard to the comments made by the reviewers: Vladislav, do you have the time to carry out the modifications requested by the reviewers ? I expect a.o. that reviewers will ask to move SCST's configuration pseudofiles from procfs to sysfs. Bart Van Assche. - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
