Scalability

[Poornima Shankar]

Horizontal scalability by definition means adding more servers to the application. and Vertical scalability is achieved by creasing resources like memory, Harddisk processor etc.

My question is does horizontal scaling automatically demands verical scaling?

Can some one analyse what exactly it means "adding servers" in horizontal scaling?

[ananth krishnan]

No. Horizontal scaling is something like adding extra webservers, adding new application servers to the clusters etc... there by increasing the scability. This is costlier when compared to vertical scaling.

Vertical scaling means that you increase the power of CPUs, RAMs in the existing hardware/systems. This may not scale well when compared to horizontal scaling.

[Poornima Shankar]

when u say adding web/app servers did u mean to say without increasing the existing hardware inorder to accomodate the new addition?
Hows that possible?

[Vishnu Ramesh]

My understanding of Horizontal scaling and vertical scaling is that in Horizontal you add additional servers ..meaning server hardware.

In Vertical scaling, you create additional instances of the application server software in the server hardware.