memory - How many web servers will I be able to run with a dual core processor?
2014-07
Jorge
This question is simple, do I need to have as many virtual machines as cores I have, or can I have more?
I plan to use my current PC as server, it is a Core 2 Duo E8400 @ 3.0, 4gb DDR2 (could buy 4 more), and 500GB sata disk.
I will host some web servers for me, for testing and perhaps some "home made" production servers.
I will use only linux.
This question is a very difficult one to answer. We don't know which linux, which web server, which modules, which (if any) database service, how many sites, how many concurrent users, how intensively used the site will be by an average user, whether there will be statistics and reporting processes (eg analytice) running in the background, whether its static or dynamic content, which content managers, how graphics/media intensive, whether there are any "live elements" (chat rooms, java apps), how fast the disk you mentioned is, what speed the RAM is clocked at, how fast your internet connection is...
The list of unknowns can go on forever! Because of this, we are unable to give a real estimate of how many sites/services you could offer from this disk.
The only real advice is to start with 1 ro 2 and then build it up until you start to see a congestion problem - at which point, add more hardware, additional servers or a better net connection.
A word of advice though - the speed of the disk will have a massive impact on the speed of a web server. When doing DB lookups, the amount of data sent to teh browser is usually small - but the amount of data "sifted" through on the drives can be massive! Likewise, when seeking and loading images, web page files etc - the slowest component of most machines is the drive and a server can only truely operate as fast as its slowest component.
Hope this helps somewhat.
David Pearce
My Macbook has a 2.4 GHz dual core processor. Because it has two separate cores, that means it can execute two functions at once, right?
So does that mean each core is approx. 1.2GHz each (for a combined 2.4 GHz) or are they actually 2.4 GHz each, and therefore is effectively running at 4.8 GHz?
Dual (and quad) core processors confuse me.
Joey
Each core runs at 2.4 GHz.
Though that doesn't mean that your system is twice as fast as a 2.4 GHz single-core system. Parallelism has (in principle) at most a linear speedup but in reality it's often much slower (though still faster than a single core).
John Gietzen
To be perfectly clear, having multiple cores does NOT speed up any one program unless it was specifically designed for multi-threading.
The effect of having multiple cores is:
Each thread runs at most as fast as your core clock speed. And, parallel processing allows an application to run more than one thread at once.
This means that at most, your processing power will be double, but not on any one thread.
hanleyp
Johannes above is correct when talking about the max frequency for each core in a multi-core procesor. The frequency rating relates to each core. So, a 2.4GHz multi-core processor typically runs each processor at the 2.4 GHz max frequency. There are two exceptions (one very common and one new):
- A processor's frequency can be dynamically scaled based upon the required performance and power draw to save power when power is not needed or to lower temperature (P-State).
- Also, recent processors have a "Turbo" feature where one core runs faster than rated when other cores are not being used (Turbo Boost).
ChrisInEdmonton
Your question is about Core 2 CPUs, not Core i7. Note, though, that if you buy a Core i7 920, you will see that the CPU is a quad core processor running at 2.66 GHz. That means that each core runs at 2.66 GHz. However, due to the Core i7's Turbo Boost, the CPU may actually run at 2.8 GHz, particularly if you are running single-threaded applications.
As others have pointed out, you can't multiply the CPU's speed with the number of cores to determine how 'fast' it is, I'm just pointing out that things are actually even more confusing than that with the current generation of Intel CPUs.