Messages in this thread | | | Date | Tue, 05 Feb 2008 22:02:16 +0300 | From | Vladislav Bolkhovitin <> | Subject | Re: Integration of SCST in the mainstream Linux kernel |
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Erez Zilber wrote: > Bart Van Assche wrote: > >>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. >> >> > > Sorry for the late response (but better late than never). > > One may claim that STGT should have lower performance than SCST because > its data path is from userspace. However, your results show that for > non-IB transports, they both show the same numbers. Furthermore, with IB > there shouldn't be any additional difference between the 2 targets > because data transfer from userspace is as efficient as data transfer > from kernel space.
And now consider if one target has zero-copy cached I/O. How much that will improve its performance?
> The only explanation that I see is that fine tuning for iSCSI & iSER is > required. As was already mentioned in this thread, with SDR you can get > ~900 MB/sec with iSER (on STGT). > > Erez
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