On Tue, Jan 06, 2004 at 03:09:01PM -0800, Jimmy Wales wrote:
Gabriel Wicke wrote:
|----------- Bind DNS round robin _______|______ (multiple A records)
How well does DNS round robin work in practice as compared to a proper load balancer?
I've never tried DNS round robin because people say it sucks. But I have no actual knowledge from first hand experience. I do know that load balancing using the tools that linuxvirtualserver.org talks about works great, and gives a very good and predictable level of control.
DNS round robin sucks because it (i) doesn't provide a way to check for a servers outage and (ii) is not suited for a farm of differently sized servers.
Having a heart beat between the two servers solves issue (i). In case of the outage of one server the other server takes over the IP and both round robin IPs point to the same server.
Issue (ii) can be addressed by having similar boxes. Since those have to be purchased, this should be easy to achieve.
In the office, we ran a website using DNS RR. It was about 500,000 hits per day and 52% of the request hit the "first" server, 48% the second. We changed to HW load balancers recently since the number of web servers increased.
==Sizing==
Regarding sizing of the squid boxes: We set up internal squids for web caching and noticed that squid does not support SMP. One squid process can utilize only one CPU. My proposed sizing:
1 CPU at about 2GHz 2 GB RAM 2*36G 15kRPM SCSI Disks Remote controller (rILO, eRIC) for remote "lights out" management 1 Unit rack mountable redundant power supply
Being most familiar with Compaq's Intel servers, I configured the box in their webshop and it was about 4,000$
Regarding CPU size: http://web.archive.org/web/20030605225127/hermes.wwwcache.ja.net/servers/squ... states that a dual Ultra Sparc at 170 MHz was able to process 1.8 million of requests per day. This is roughly the current load of en:. A 2 GHz x86 CPU beats the Sparc by far. If we want to spend more money on the box, add memory.
Regards,
JeLuF