Machine 1: $2000 Machine 2: $2000 Machine 3: $2000 Knowing how to rig them together and maintain them in a fully fault- tolerant way: priceless.
(Sorry for the off-topic post, I couldn't resist). -- Mark Lewis On Wed, 2006-02-15 at 09:19 -0800, Craig A. James wrote: > Jeremy Haile wrote: > > We are a small company looking to put together the most cost effective > > solution for our production database environment. Currently in > > production Postgres 8.1 is running on this machine: > > > > Dell 2850 > > 2 x 3.0 Ghz Xeon 800Mhz FSB 2MB Cache > > 4 GB DDR2 400 Mhz > > 2 x 73 GB 10K SCSI RAID 1 (for xlog and OS) > > 4 x 146 GB 10K SCSI RAID 10 (for postgres data) > > Perc4ei controller > > > > ... I sent our scenario to our sales team at Dell and they came back with > > all manner of SAN, DAS, and configuration costing as much as $50k. > > Given what you've told us, a $50K machine is not appropriate. > > Instead, think about a simple system with several clones of the database and > a load-balancing web server, even if one machine could handle your load. If > a machine goes down, the load balancer automatically switches to the other. > > Look at the MTBF figures of two hypothetical machines: > > Machine 1: Costs $2,000, MTBF of 2 years, takes two days to fix on average. > Machine 2: Costs $50,000, MTBF of 100 years (!), takes one hour to fix on > average. > > Now go out and buy three of the $2,000 machines. Use a load-balancer front > end web server that can send requests round-robin fashion to a "server farm". > Clone your database. In fact, clone the load-balancer too so that all three > machines have all software and databases installed. Call these A, B, and C > machines. > > At any given time, your Machine A is your web front end, serving requests to > databases on A, B and C. If B or C goes down, no problem - the system keeps > running. If A goes down, you switch the IP address of B or C and make it > your web front end, and you're back in business in a few minutes. > > Now compare the reliability -- in order for this system to be disabled, you'd > have to have ALL THREE computers fail at the same time. With the MTBF and > repair time of two days, each machine has a 99.726% uptime. The "MTBF", that > is, the expected time until all three machines will fail simultaneously, is > well over 100,000 years! Of course, this is silly, machines don't last that > long, but it illustrates the point: Redundancy is beats reliability (which > is why RAID is so useful). > > All for $6,000. > > Craig > > ---------------------------(end of broadcast)--------------------------- > TIP 5: don't forget to increase your free space map settings ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
