What exactly is vertical scalability?

graziazi used Ask the Experts™
Hi. As regards the area of multi-tier architecture and scalability, what does vertical scaling mean? I read definitions such as 'Vertical scaling - services are scaled within the system', but this makes no sense to me.

I can see the sense in horizontal scaling, because it happens within the same tier and flexible replication can take place. But form what I read about vertical scaling I don't understand the benefits, nor really what happens
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the short and sweet of it

There are two "scales" Verticle and horizontal:

Verticle also reffered to as scaleing up involves upgrading a single "node" with more Ram Cpu etc
Horizontal also reffered to as scaling out invloves adding more nodes
Sr. AIX Admin
Why vertical scaling?
Adding ram/cpu to a system to support more work, may be a lot cheaper, than buying/licensing another system horizontally.

Vertical scaling can be for fat multi-threaded applications, where you may start with a smaller 2way system image/virtual guest, and either through physical changes, or virtual re-configuration, you add resources to the environment the application is running in, VMware, or IBM Lpar for example.  

So, a <<WEB>>  <<APP>>  <<DB>>  three tier app.  You may run a POC with fairly small configuration.  Then, liking the results, you add another web and app horizontally for redundancy.  Then, as demand grows, you add more cpus/ram to the various tiers to support more work within each tier (Vertically).

TomuniqueSr. AIX Admin

Also to note.  
Conversely, someone may ask: What DOESN"T scale vertically?  
Some vendors may say their app can scale vertically, but if that translates to just RAM/CPU additions, then who can't do that?

Answer:  Single threaded 32bit apps.   You can add 16G ram, they can't reach it.  You can add 16CPUS, and they'll only keep 1 busy.
          You MAY be able to run multiple copies on a single machine, but, that's basically a form of horizontal scaling.  Without some way to distribute work to those other processes, they won't be kept busy either.


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