On Tue, 2008-02-05 at 16:11 -0800, Nicholas A. Bellinger wrote: > On Tue, 2008-02-05 at 22:21 +0300, Vladislav Bolkhovitin wrote: > > Jeff Garzik wrote: > > >>> iSCSI is way, way too complicated. > > >> > > >> I fully agree. From one side, all that complexity is unavoidable for > > >> case of multiple connections per session, but for the regular case of > > >> one connection per session it must be a lot simpler. > > > > > > Actually, think about those multiple connections... we already had to > > > implement fast-failover (and load bal) SCSI multi-pathing at a higher > > > level. IMO that portion of the protocol is redundant: You need the > > > same capability elsewhere in the OS _anyway_, if you are to support > > > multi-pathing. > > > > I'm thinking about MC/S as about a way to improve performance using > > several physical links. There's no other way, except MC/S, to keep > > commands processing order in that case. So, it's really valuable > > property of iSCSI, although with a limited application. > > > > Vlad > > > > Greetings, > > I have always observed the case with LIO SE/iSCSI target mode (as well > as with other software initiators we can leave out of the discussion for > now, and congrats to the open/iscsi on folks recent release. :-) that > execution core hardware thread and inter-nexus per 1 Gb/sec ethernet > port performance scales up to 4x and 2x core x86_64 very well with > MC/S). I have been seeing 450 MB/sec using 2x socket 4x core x86_64 for > a number of years with MC/S. Using MC/S on 10 Gb/sec (on PCI-X v2.0 > 266mhz as well, which was the first transport that LIO Target ran on > that was able to reach handle duplex ~1200 MB/sec with 3 initiators and > MC/S. In the point to point 10 GB/sec tests on IBM p404 machines, the > initiators where able to reach ~910 MB/sec with MC/S. Open/iSCSI was > able to go a bit faster (~950 MB/sec) because it uses struct sk_buff > directly. > Sorry, these where IBM p505 express (not p404, duh) which had a 2x socket 2x core POWER5 setup. These along with an IBM X-series machine) where the only ones available for PCI-X v2.0, and this probably is still the case. :-) Also, these numbers where with a ~9000 MTU (I don't recall what the hardware limit on the 10 Gb/sec switch lwas) doing direct struct iovec to preallocated struct page mapping for payload on the target side. This is known as RAMDISK_DR plugin in the LIO-SE. On the initiator, LTP disktest and O_DIRECT where used for direct to SCSI block device access. I can big up this paper if anyone is interested. --nab - 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
