Load-balancing seems to come up a lot on this list, and in my own configuration. Its also rather difficult to do at an "ideal" level, as the load is session-based. By that, I mean when a user logs in, s/he does so on a specific server, and for the duration of that login, the session cannot be moved to another server. As a result, "true" load-balancing is not obtainable with current technologies. (This discounts OpenMosix-style load balancing, which in theory would work well, but my understanding is that in practice, it leaves much to be desired.)
About the best solution I've seen is to distribute the XDMCP sessions between the servers. This is where the pair of servers, all running DHCP and configured as a "standalone" server comes into play. Unfortunately, this only load-balances on terminal boot. That terminal will use the same server until its rebooted. Perhaps a better solution would be to modify the startx screen script to be able to take a list of XDMCP servers, and every time it starts a connection, it does a ping of sorts, taking into account load, on the server list and connects to the least-loaded server. To provide better balancing, I'd make it re-evaluate its decision while sitting at the login screen periodically, if possible (once a user is logged in, no point in evaluating anything). I suspect the first part is quite doable. I remember seeing "older" xdmcp servers putting out load info such that Xterms running in query mode would display a list of servers and their load. Thoughts? --Jim On 10/11/07, Alistair Crust <[EMAIL PROTECTED]> wrote: > On Thu, 2007-10-11 at 11:46 +0200, Anselm Martin Hoffmeister wrote: > > Am Freitag, den 05.10.2007, 14:33 +0100 schrieb Alistair Crust: > > > Hi, > > > I've been puzzling over the problem of load balancing for some time and > > > I've come up with an idea. > > > > > > Our current setup here is that we have 1 nis/nfs server for > > > authentication and sharing of /home, and we have 3 ltsp servers each > > > with dhcpd/tftpd/xdmcp. > > > > > > Here the server that is under the least load will/should reply to dhcp > > > requests first (all terminals are hardcoded an ip using mac address), > > > each ltsp server then authenticates and mounts /home from the central > > > server. Works ok, but not very pretty. > > > > > > Now my idea now (and I really don't know if this is going to work) is to > > > have 1 dhcpd server (maybe 2 using dhcp failover as described int the > > > dhcp3 docs) and then load balance the tftp services. > > > > > > So my question is: once the client has gotten the pxe image from one of > > > the 3 servers and starts to boot will it use this server to mount its / > > > directory on and connect to its xdmcp service? > > > > > > Any thoughts? > > > > > > > TFTP services are not related to any other service. So if, for example, > > you load balance TFTP between servers "linux1" and "linux2", the thin > > client, once booted, will not "remember" which server it was booted > > from. The NFS-Server to be used is determined by the "root path", and > > the XDMCP login server to be used by the appropriate configuration file > > setup. > > > > You could load-balance DHCP (especially for redundancy; the CPU load is > > not too much of concern there), and have each of your two DHCP servers > > request TFTP download from the same machine: Thus, if one of those > > servers crashes, the other will hand out valid boot info. > > > > Load balancing the sessions (which IMO is far more important) is done by > > other means, namely the XDMCP configuration and all around there. > > > > BR > > Anselm > > well my main concern is that I retain the ability to use Local Disk > Access. > > bullet pointed I would like to: > > * Have one/two servers for definitive dhcpd (I can use failover dhcp for > redundancy with two servers) > > * Split the client connections evenly over all "available" terminal > servers (brings both load balancing and failover) > > * Retain the ability to use Local disk access, sound etc. > > My idea above was to try and pick a common point to split the load and > have the ability for failover. I just don't know enough about how that > all goes together to make it work. > > > -- > ----- > Kind regards > Alistair Crust > Systems Administrator > Skegness Grammar School > Vernon Road > Skegness > PE25 2QS > TEL: 01754 610000 (ext'852) > FAX: 01754 896875 > > > ------------------------------------------------------------------------- > This SF.net email is sponsored by: Splunk Inc. > Still grepping through log files to find problems? Stop. > Now Search log events and configuration files using AJAX and a browser. > Download your FREE copy of Splunk now >> http://get.splunk.com/ > _____________________________________________________________________ > Ltsp-discuss mailing list. To un-subscribe, or change prefs, goto: > https://lists.sourceforge.net/lists/listinfo/ltsp-discuss > For additional LTSP help, try #ltsp channel on irc.freenode.net > ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _____________________________________________________________________ Ltsp-discuss mailing list. To un-subscribe, or change prefs, goto: https://lists.sourceforge.net/lists/listinfo/ltsp-discuss For additional LTSP help, try #ltsp channel on irc.freenode.net
