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Best Solution For HA and Network Load Balancing?
supaneko writes "I am working with a non-profit that will eventually host a massive online self-help archive and community (using FTP and HTTP services). We are expecting 1,000+ unique visitors / day. I know that having only one server to serve this number of people is not a great idea, so I began to look into clusters. After a bit of reading I determined that I am looking for high availability, in case of hardware fault, and network load balancing, which will allow the load to be shared among the two to six servers that we hope to purchase. What I have not been able to determine is the 'perfect' solution that would offer efficiency, ease-of-use, simple maintenance, enjoyable performance, and a notably better experience when compared to other setups. Reading about Windows 2003 Clustering makes the whole process sounds easy, while Linux and FreeBSD just seem overly complicated. But is this truly the case? What have you all done for clustering solutions that worked out well? What key features should I be aware for successful cluster setup (hubs, wiring, hardware, software, same servers across the board, etc.)?"
1000+ unique visitors is nothing. Even if they all hit the site at lunchtime (1 hour window), and look at 30 pages each (very high estimate for a normal site) that's only 8 requests a second. That isn't a lot. A single server could cope easily, especially if it's mostly static content. As an example, a forum I run gets a sustained 1000+ users an hour and runs fine on one server.
As for "high availability", that depends on your definition of "high". If the site being down for a morning is a big problem then you'll need a redundant failover server. If it being down for 15 minutes is a problem then you'll need a couple of them. You won't need a load balancer for that because the redundant servers will be sitting there doing nothing most of the time (hopefully). You'll need something that detects the primary server is offline and switches to the backup automatically. You might also want to have a separate database server that mirrors the primary DB if you're storing a lot of user content, plus a backup for it (though the backup DB server could always be the same physical machine as one of the backup webservers).
Whoever told you that you'll need as many as 6 servers is just plain wrong. That would be a waste of money. Either that or you're just seeing this as an opportunity to buy lots of servers to play with, in which case buy whatever your budget will allow! :)
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If the site goes down do you lose truck loads of money or does anyone die? Load balancing and HA sounds a little overboard for a site with a thousand visitors a day. A hundred thousand and you can probably justify the expense. I would probably just be looking at a hosted dedicated server somewhere for now.
there is also more of them than you can poke a stick at and prices are very reasonable. places like rackspace for this kind of thing for $100/mo.
the other advantage is you don't need to pony up for the hardware.
If you mod me down, I will become more powerful than you can imagine....
Why are you purchasing six or so servers before you even have one online?
You say that you expect "1,000+ a day" visitors which frankly is nothing. A single home PC with Apache would handle that.
This entire posts strikes me as either bad planning or no planning. You're flirting with vague "out of thin air" projections that are likely impossible to make at this stage.
Have a plan in place for how you will scale your service *if* it becomes popular or as it becomes popular but don't go wasting the charities money just in case your load jumps from 0 to 30,000+ in 24 hours.
Lets get more blunt. Depending on what you are doing and if you want to worry about failover then 1000 a day is bugger all. Simple set up of Apache and Tomcat (if using Java) with running round-robin load-balancing will give you pretty much what you need.
If however you really are worried about scale up and scale down then have a look at Amazon Web Services as that will probably more cost effective to cope with a peak IF it occurs rather than buying 6 servers to do bugger all most of the time.
2 boxes for hardware failover will do you fine, if you are worried about HA the its the COST of downtime that you are worried about (i.e. down for an hour exceeds $1000 in lost revenue) which will justify the solution. Don't just drive availability to five nines because you feel its cool, do it because the business requires it.
An Eye for an Eye will make the whole world blind - Gandhi
16GB? Are you mad? Anything beyond 1GB should be enough to handle 1000 unique visitors per day. If you want to virtualize the system and have a separate web- and database server, 2GB should be enough already, if you ant to go further and have a separate virtual mail server in there, 2GB is still sufficient and 3GB is plenty.
There is no way to be fully redundant unless you have independent power sources, which usually requires your backup systems to be geographically separated. In my experience, loss of power is the single most common reason for a system failure in a well designed system (after human error that is).