Quanah Gibson-Mount wrote: > > > --On Thursday, October 12, 2006 9:04 PM +0200 Michael Ströder > <[EMAIL PROTECTED]> wrote: > >> HI! >> >> I support Giovanni's statement that fail-over should preferrably be >> implemented in LDAP clients. Because the client really knows what to do >> if all fails. In practice this means to really teach the developers hard! > > Sadly, Stanford has plenty of proprietary software that accesses our > LDAP servers. > >> Regarding TCP-level load-balancers: Typically the servers are located in >> one data center. IMHO this works quite well for most read-only >> applications. If you need fail-over for write requests you either need >> multi-master replication (with lack of data integrity) or some sort of >> hot-standby server which completely takes over the service. >> >> Also with using proxy servers for balancing the requests you should >> carefully think about your network topology to avoid WAN traffic to >> other data centers. >> >> If you'd like to implement fail-over between different locations >> probably DNS gets involved. But not simply DNS round robin! > > > Stanford uses a software load balancer to a pool of replica systems (in > our case, we have a single source system for all writes, so we don't > worry about applications writing to the directories). The main issue > I've found with using the software load balancer is that Java caches the > returned IP, so you need to do some junk to get it to do retries if the > connection to the system it is talking to fails. > > The software we use lets you run external commands on each individual > system that help determine the weights, so it is more than simple DNS > round robin. For example, in Stanford's case, we have it run a local > ldapsearch to verify slapd is running. If it is successful, then it > uses the system load to determine the weight. If it is unsuccessful, it > makes the weight extremely high, essentially dropping it from the pool. > > --Quanah > > -- > Quanah Gibson-Mount > Principal Software Developer > ITS/Shared Application Services > Stanford University > GnuPG Public Key: http://www.stanford.edu/~quanah/pgp.html > > --- > You are currently subscribed to [email protected] as: > [EMAIL PROTECTED] > To unsubscribe send email to [EMAIL PROTECTED] with the word > UNSUBSCRIBE as the SUBJECT of the message.
can i ask what you use for your software based load balancer linux lvs or is it a "stanford" in-house application. _Terry --- You are currently subscribed to [email protected] as: [EMAIL PROTECTED] To unsubscribe send email to [EMAIL PROTECTED] with the word UNSUBSCRIBE as the SUBJECT of the message.
