That is one great explanation of fiber. Last time I worked with fiber it was 100mb RAID with a couple of cabinets for storage. My brain hurts thinking about what is happening now. Sam. Ted S. Letofsky wrote: >Hey all, > >Fibre channel at the drive level is a single 40 pin copper connector. >However, unlike scsi, you don't often see single backplane devices to plug >the drives into. > >That 40 pin connector supports two logical and physical "loops". > >So... > >Fibre devices (be it a jbod or an array or raid) often have two ports, an >"A" port and a "B" port built into them. > >There is a 1GB standard and a 2GB standard (4GB and 10GB are already on the >roadmap and/or in limited production for switches and cards and drives) > >You can have up to 126 devices on a fibre bus in "loop" mode (arbitrated >loop) and then it acts like scsi but can be set up to "self configure" or >you can use the chassis for drives to "SET" the loop id, aka the "ALPA" > >There is also a "fabric" mode where everything gets identified by it's >"world wide name", which is the fibre channel equivalent of a MAC address. > >Then the basic limit is 16 million addresses. > >You can do fabric mode with arrays and raids and libraries, but not easily >with regular jbod or disk drives connected to cards because in that limited >environment. > >There are fibre channel hubs, and fibre channel switches, and both concepts >are exactly the same as in ethernet, and for basically the same reasons. >However, almost all switches in fibre channel are managed for zoning, etc... > >The interface, (copper or glass) makes no difference for fabric or loop mode >(you will also here people say "point to point" mode which is fabric >negotiation even in a "loop" topology, like when plugging a fibre channel >raid directly into a server card. > >The 1GB fibre standard for copper was/is either a db9 connector with 4 pins >uses, or an HSSDC connector, which looks more like a squished and wider >ethernet port. > >The optical 1GB fibre standard looks the same as the original optical 1GB >standard for ethernet, and is called an "SC" connector. > >The 2GB standard for optical is called LP, and is about 1/3rd the size, and >uses the same style of connectors that the newest optical ethernet does, >although the ports and cards and switches themselves are not usually >interchangeable. > >There is a copper standard for 2GB but is rarely used and called HSSDC2. > >The last confusing thing is that some cards and switches and chassis use >EMBEDDED ports and some use removable/replaceable ports. >In 1GB, they call them "GBIC"s, and for 2GB they are called "SFP"s ><shrug> > > >So, the fibre standard allows for "daisy chaining" like SCSI does. >As long as you have fewer than 126 devices on the loop. That doesn't mean >you'll get good performance. <grin> >Raids count as ONE device on a loop, if connected in loop mode. > >In general, if you are going to do LOOP things, you try to keep 16 or so >devices on the bus. >If you want lots of devices, use a hub. >If you want/need more bandwidth, use a switch and/or use more fibre host >adapters. <grin> > >Ted Letofsky ><not a very good linux guy, but I know a little storage> > >-----Original Message----- >From: tclug-list-bounces at mn-linux.org >[mailto:tclug-list-bounces at mn-linux.org] On Behalf Of Nate Carlson >Sent: Thursday, May 26, 2005 12:29 PM >To: Florin Iucha >Cc: tclug-list at mn-linux.org >Subject: How does Fibre Channel work? [Was: Re: [tclug-list] Source >forQLA2200's locally?] > > >On Thu, 26 May 2005, Florin Iucha wrote: > > >>If I want to connect three computers to an array, do I need a switch? >>Does an array have a single port? (+ see below) >> >> > >Again, this is from my limited experience. > >All of the arrays I've worked with have two ports, which both connect you >to the same loop. However, I know there are arrays with more ports, and >arrays with only single ports. > > > >>I remember something about an "Arbitrated Loop" where the computers >>and >>storage sit in a circle and pass a pipe ;) Can I do that with copper, or >>do I need something optical? >> >> > >Quick google search: > >http://www.seagate.com/support/kb/disc/fcp.html > >Doesn't explain it all that well, but as I understand it, the switch or >hub is what allows your computer to connect to the loop of drives. > >Please, someone correct me if I'm wrong! :) > >------------------------------------------------------------------------ >| nate carlson | natecars at natecarlson.com | http://www.natecarlson.com | >| depriving some poor village of its idiot since 1981 | >------------------------------------------------------------------------ > >_______________________________________________ >TCLUG Mailing List - Minneapolis/St. Paul, Minnesota tclug-list at mn-linux.org >http://mailman.mn-linux.org/mailman/listinfo/tclug-list > > > >_______________________________________________ >TCLUG Mailing List - Minneapolis/St. Paul, Minnesota >tclug-list at mn-linux.org >http://mailman.mn-linux.org/mailman/listinfo/tclug-list > > >