2 Apache web servers with identical vhosts to serve a few hundred clients. RHEL 6 on all boxes. What are the pros and cons to having a load balancer with a VIP, and pointing all of the DNS A records to the VIP vs having no load balancer in front and just using 2 A records for each site, one with server A IP, and the other with server B.
closed as primarily opinion-based by Wesley, Sven♦, Jenny D, Dave M, Ladadadada May 4 '14 at 20:12
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Pro for dedicated load balancer:
It actually can balance the load (depends on the software of course).
You can disable a backend node without anyone noticing it.
If a node crashes only the current connection dies (if at all) and the next request from the same client goes to a different node (vs. the client caches DNS and hits it again and again).
Pro for DNS round robin?
I don't know. It's cheap I guess.
@faker has a good answer. i would comment to that, but my rep does not allow. a couple of additional pros for each:
- can reliably scale (dns cache can delay RR scaling)
- in most cases, you can have a heterogenous cluster with machines of different capabilities - with RR, you are only as strong as your weakest link
- likely marginally faster, since there's less routing
- one less point of failure (less true if you are using a managed lb like AWS ELB)
Pros of RR dns:
Cons of RR dns:
- in case of host failure, you loose all the traffic while restoring it (or at least the time of dns propagation for a new ip)