Some big concerns include:

a) Secure transfer of your data – No external attacks while the transfer of data from/to the cloud.

b) Location of your data – Geographical location of data.

c) Control of your data – Who has access to your data?
Cluster is defined as a large group of computers that merge their capabilities and work as one. This aggregating of computational power is also called clustering of services. Each cluster is then referred to a single node in computing terms.
A data center can be thought of as a collection of servers which hosts applications and storage space. Physically, a data center can be a big room full of servers that can be accessed from anywhere in the world via the internet.
The two biggest concerns for a Mobile client are:

a) Security of data

b) Speed of data transmission
This model has the following advantages:

a) There is a large audience for this model.

b) It is highly fault-tolerant.

c) HTTPS-encrypted access provides privacy.

d) Many provider options are available.

e) It is cost-effective.