Hi Marhsall et al., On Thu, Dec 04, 2008 at 09:40:07AM -0800, mhampton wrote: > Having taught several classes using Sage, I highly recommend setting > up a server (or possibly more than one if you have a lot of > students). I tried setting up one sage instance per machine in a lab > with macs, and it was a real pain to administer. There are quite a > few advantages of having a small number of servers:
I agree with this in your setting, but would like to give a parallel view in 1) the low-bandwidth and resource-starved developing world, and 2) certain class environments, e.g. ours where the students live-in, have no laptops, bandwidth. > 1) Remote access. In my experience students really like the option of > working outside of school, and being able to pick up where they left > off. Since we don't have a nice license for student copies of > mathematica, this is one area where students love Sage compared to > mathematica. We don't provide Mathematica. Partly because of our policy to work with Free Software, partly because it is too expensive -- we don't see the point of "demo", "student" versions, or "limited" licenses. Each students should be able to do all the work. In many places price is simply the limiting factor. Then SAGE is not a 'viable alternative', it's all that we have. > 2) Group work. If you have small groups they have share worksheets if > they are on the same server. It also makes it easy for students to > remotely ask questions, i.e. they can share their worksheet with you > and you can troubleshoot or help from the comfort of your home or > office :) Agreed. In our situation the students live-in, work in the lab 24 hours, as it is in teh same building as the accomodation, and bandwidth does not allow convenient remote sharing. Due to the campus growing (from one building to three) there is definitely room for 'remote' usage coming up. Those who do have a laptop (rare) can install sage. None of the machines in the institute run windows, and all student laptops dual boot windows/ubuntu. > 3) Easier to maintain. If you want to upgrade the sage version, its > much easier with 1-4 servers than a sage copy per machine. If you do not image your machines, you are already doing something wrong. It is easier for me to maintain one desktop image (I use systemimager, ghost and others do the same) rather than four servers. OK, so I'm the system admin not the maths lecturer, who may want to stay away from system admin, but then it may be good if you have a system admin to do this. Servers have to be backed up -- I have 100 client machines that are identical with central storage/passwords, so if one dies the functionality is not gone or 25% or 50% reduced. You just move to another PC. If it crashes, or there is a security problem, only one user is affected, and it is easily repaired too > 4) Might be faster than a VM version, although this of course depends > on hardware. > I run my sage servers off of an aging mac pro (quad core 2.66 GHz with > 8 GB of RAM) and a couple of linux (AMD quad-core) workstations which > are also about 2-3 years old. Each of those can handle about 20 > students with no problem. If the load is spread out (i.e. not > everyone in a lab at the same time) they could probably handle 30-40 > students each. The machine with the most RAM is 3GB file server. All desktops here have 512M. OK, they're all due for replacement next July, probably I can go for 4G per PC then. There aren't really "aging" machines lying around to be used that have > 512M RAM. Luckily one got stolen, and I can claim a new desktop in the meantime. A new intel board, duo core chip, 4G RAM box will do nicely as a SAGE server in the corner. (However, now I need backups again, but OK, RAID 1 and a sage data rsync to another box will do). If your 8G machines are not handling 30-40, well it bodes much better for me to stick to a sage instance on each machine, so that my 512M only has to deal with one user. If anyone wants to donate hardware or money to buy hardware for www.aims.ac.za, mail me off-list please :) I need $100,000 to upgrade all desktops for the next 4 years, $20,000 for servers, etc. etc. > One problem is that students tend to leave their worksheets running, > which starts eating into the RAM available. I should probably use the > "timeout" option in my notebooks, which would solve that problem. Avoided completely with sage instance per machine. Well, here we have the special case that the lab is large enough for a PC per student, so students just screen-lock their desktops anyway. Granted, some of it is a special case (live-in situation, easy secure lab access in the building), but the low resources (bandwidth, "aging" machines with 8GB RAM!!) are not a special case, that is the norm. In fact, what I have seen at departments across Africa is that the norm is no network storage (I don't call an icon in the corner of the screen network storage -- when the electricity fails, as it does, the little UPS keeps your PC up but the switch is off already so you can't save centrally -- nobody really uses it) and there is often not a very good SSI (single sign on, the point here not the single password, but the identical, redundant environment so that when hardware fails you can just move along one seat). Without those, the environment to include SAGE in the desktop image is not really available. > I email my students the IP address and port, or tell them during > class, and of course use the secure option, and I haven't had any > security problems yet. Some of my servers are on a VPN network which > makes them a little more secure too. I think during the next few years as bandwidth increases, this will become a reality, and I will want to upgrade an (not-yet-existant) SAGE server from a 4G-RAM PC for $1,000 to a 16G RAM proper server for $10,000, but only usage will determine that need to be there. Then I can have 500 non-regular off-site users, 50 regular off-site users, and perhaps 70 concurrent and regular on-site users, and it will be most important that SAGE take logins and passwords from our LDAP directory. I believe some work was done on this, I remember a thread on sage-* some time ago. I can then also ask the national high performance computing facility (www.chpc.ac.za) to install SAGE -- they gave me a login for that purpose, but the details will be hard so it has been stalled ever since. 1. there are legal indemnity forms to sign, etc, I cannot just open it to my LDAP tree, projects have to be registered and agree with their mandate, they force a 6 monthly password change, you may not hack blah blah. 2. They'd rather just run the python processes, sage server, on the HPC, and the web server elsewhere. Bandwidth is good there, but not elsewhere. Their firewall settings are very restrictive though I suppose I could tunnel over ssh, but this starts being against their policues in (1) above... 3. Perhaps only large jobs can be sent there. The way the cluster works entire hosts are assigned to jobs until completion, and we cannot lock up 20 of the 40 hosts with students' worksheets. However we can look at restricting this to advanced researchers with registered projects, the way they usually work, and not for teaching at an introductory level. We didn't get much further than those obstacles, and we will pursue it when there is a greater demand. At the moment I'm still promoting SAGE, nobody is clamoring for it -- they don't even know what it is. It's a bit different for me as a sysadm at a maths institute, with many short visitors whose code we often had to port matlab -> octave, nowadays whatever -> scipy, and (in future whatever -> sage?) though these are small codes for teaching. I figure most people reading this are maths lecturers, who don't really want to do system administration. Even from my point of view the power and flexibility and future of sage is clearly a web interface, shared notebooks, etc. but my current situation forces me to have one per PC. regards, Jan -- .~. Jan Groenewald /V\ IT Manager /( )\ +27 21 787 9328 ^^-^^ www.aims.ac.za --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sage-edu" group. 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