Infrastructure Scaling-up Vs. Scaling-Out.

It is quite common in web applications or distributed hosted systems to look at issues in scaling your platform to either support more clients or processing speed/power.

There are 2 approaches to upgrading your hardware.

• Scaling-up  - the process where a single ‘Iron Server’ is upgraded to a maximum load. This means you upgrade a server to support the maximum CPU/RAM allowed. On Some bare bone ‘Iron Servers’ these statistics can be quite impressive for example a HP Proliant DL785 G5 can be upgrade to 8 CPU sockets, 64 memory sockets, 16 drive bays, 11 potential expansion slots and 6 power supplies to provide the server power.
• Scaling-out – This is where a moderate powered server based setup is augmented by adding more equivalent powered servers Ideally with exactly the same architecture or specification although technology advance make this hard over time.

With the advent of cloud computing hitting a more mainstream market and some proven viability. It is actually quite natural to look at scaling-out a system to take advantage of this newer parallel processing paradigm.

Now there are issues you need to be aware of in both scenario’s so lets start with the obvious issues and yes all are mainly TCO/ROI based points for now. Later I will do some posts on the development and systems impact of these ways of achieving physical scalability. ( I am listing negatives only ).

Scaling-UP

• Cost can be quite prohibitive for a single server albeit a monster as the HP Proliant can be when fully loaded.  (I have seen some priced at over 125K+ GBP (200K+ USD)
• Potentially a single point of failure
• Not as optimized for parallel processing as am array/gird of servers and does not scale the same
• Physical limit on scaling (cpu/ram/storage) storage can be made external so is not an issue.

Scaling-Out

• Rack Space/Server space costs more
• Power consumption can be higher for same amount of processor/memory when compared to a scaled-up iron server
• OS and Database Licensing costs can be a lot more expensive, however this is changing with cloud database and application servers.
• Infrastructure to support and manage the servers can cost a lot in both time and money.

Final notes, if the real issue is cost; Although scaling-up seems more expensive do not underestimate the sheer amount of resource costs in supporting many servers, storage of the servers, network infrastructure and so on. The only time scaling out seems to make a real case on cost is when you have a critical mass in scaling to meet client needs, and even then you can cloud/cluster a collection of “iron servers”

Personally, it depends on the situation you are faced with, if cost is an issue but you have some good network infrastructure clouding with a array of servers is a very viable options. But one you start to scale it maybe worthwhile just getting an iron server or 2 and scaling them up in the same network. – Scaling out is really useful when you have a lot of old servers/pc’s that are already inside your infrastructure and can be utilized even if just a little by a cloud or grid based solution.

I have purposely kept aware from the area of server virtualization and provisioning as it can change things drastically. This is also why I have avoided the issue of OS choice as well.