Difference between Private Cloud and public cloud
The only difference between public and private clouds seems to be ownership. Is there any other distinction that is relevant and important for users to understand?
Answer
Public Cloud
A public cloud is offered as a service, usually over an internet connection.
Public clouds typically charge a monthly usage fee per GB, combined with bandwidth transfer charges.
Users can scale the storage on demand and do not need to purchase storage
hardware.
Service providers manage the infrastructure and pool resources into capacity that customers can claim.
Private Cloud
Private clouds are deployed inside a firewall and managed by the user organization.
Private clouds are built from software running on customer supplied commodity hardware.
The data is typically not shared outside the enterprise and full control is retained by the organization.
Factor to Consider to differentiate private and public cloud
Initial investment
Private Cloud
There is often an assumption that private clouds require a million dollar capital outlay and an investment in volumes of equipment.
The reality is that private clouds can be built for under $5,000 and deployments are simple. Users can download software and have a cloud running in under an hour.
Public Cloud
Public clouds can start as low as $1000
For example, a public cloud makes it easy to backup a single laptop or deploy an application starting at a few GBs. As a company grows, it can lease more
capacity and the cost scales linearly.
Longevity of data
Public cloud
As data ages within the public cloud, the cost continues to rise.
If you are publishing frequently changing or short lived content such as movie trailers or daily newscasts, the flexibility of a public cloud is a good solution.
Private Cloud
Private clouds are licensed like enterprise software
Longevity of data does not increase the cost of the solution which bodes well for archive or content repository applications.
Required performance
Public cloud
Public clouds are accessed over the internet and face the limits of both your and the provider’s bandwidth connection.
This is usually capped around 10MB/s
To scale performance you can initiate additional 10MB/s connections, but doing so increases the bandwidth charges.
Private Cloud
Private clouds are deployed inside the firewall and accessed over the Ethernet LAN at wire speed
It is not uncommon to have read access in the 100 MB/s range per node. Adding nodes
provides additional performance to the cloud.
Files can be replicated to many nodes, each of which can serve requests independently.
Access patterns and locations
Public Cloud
Public cloud offerings typically include replication of data to multiple geographically dispersed locations, sometimes for an extra fee
If your users are global and can benefit from locality of data, a public cloud can sometimes substitute for a content distribution network
Private Cloud
Private clouds are typically deployed in a single location for LAN based access.
Remote users will need to connect over the WAN and work with internet type latencies.
Larger private cloud deployments can include multiple locations and start to approach the public cloud distribution, albeit at a higher initial investment.
Security and data isolation
Public Clouds :
There are many published opinions and dedicated websites that cover security of public cloud offerings. The bottom line is it comes down to control of your data. Public clouds are just that–public.
Isolation of data is only as strong as the virtualization technologies used to build the
cloud and the provider’s firewall.
If you are at all concerned about the data being outside of your company it should not be in a public cloud.
Private Clouds
Private clouds are owned, deployed and managed by internal employees.
Data is isolated based on your requirements and security is based on internal processes
Confidentiality and destruction of data
Public Clouds
Similar to security, confidentiality of data is a factor to consider when choosing a cloud storage solution.
The law is defined based on control of the data.
If the service provider is subpoenaed for your data based on their control of the data, they must comply regardless of your knowledge or objections.
Private Clouds
With private clouds you maintain control and have input, or at least knowledge of legal activities.
When it comes time to destroy or delete the data, it is in your power and can be confirmed by your own team.
Service level agreements
Public Clouds
Public cloud SLAs are published by the provider and are their responsibility.
Remediation is typically a cash payment, and while they will do their best to recover data, there is no guarantee of data availability.
SLAs can also be impacted by internet connectivity. For example, if your link
goes down, you cannot access your data and there is no remediation (unless your
network provider has guaranteed uptime).
Private Clouds
Private clouds have different mechanisms for data availability and service of access.
Most leverage multiple copies of files on multiple nodes and treat each node as a failure domain.
Individual server failures do not bring down the cloud or create data loss, so most SLA
agreements are satisfied.
It is important to have a complete understanding of the architecture and its capabilities when selecting and deploying a private cloud.
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