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Enterprise Storage Battle: On-Premises vs. Cloud

Since there's no clear-cut answer for all enterprises, evaluate the pros and cons of each before making your choice.

• By Scott D. Lowe
• 05/13/2013

For many, when they think of data storage, the image that jumps immediately to mind is probably a picture of a hard disk or of a storage array sitting in the rack in an organization's data center.  If that's where the image of storage stops, it's time to expand your view!  Today, although organizations will continue to buy local storage, cloud-based storage is beginning to become a potential fit for some applications.  With cloud-based storage, an organization can purchase just the amount of storage that is needed and pay a monthly fee for that storage rather than having to buy an expensive on-premises hardware device that may carry a high initial capital cost.

Of course, as in all things, the devil is in the details.  While cloud storage may be an intriguing emerging option, there are good things and bad things when it comes to cloud storage versus on-premises storage hardware.  This post explains some of those pros and cons, and explains what kinds of services might benefit from the different kinds of options that organizations have at their disposal.

On-Premises Storage
On-premises storage arrays are pretty well known entities with some pretty well known pros and cons, although the changing face of enterprise storage is mixing things up a bit. That said, here's a look at some good and some bad regarding on-premises storage:

As mentioned, on-premises storage is well established, well understood infrastructure.  These devices can provide organizations with very fast storage backed by fast storage networking communications, making on-premises storage suitable for a number of different kinds of workloads that require high performance, low latency storage, such as server and desktop virtualization, database applications, Exchange, and the like.

Being able to achieve low levels of latency is perhaps one of the greatest benefits to on-premises storage.  The further away that storage resides, the higher latency figures that will be suffered; many applications will not operate properly in high-latency conditions.

On the downside, on-premises storage can carry with it pretty significant upfront costs.  Most organizations buy expensive SANs and then depreciate them over a number of years.  In addition, there are several other costs that need to be considered as it pertains to the total cost of ownership of storage.  These include additional licensing costs for desired features, ongoing annual hardware/software maintenance, electricity and personnel to manage the system.  In total, a storage array, when considered in whole, can be an incredibly expensive investment, but also one that is critical to the company's needs.

Cloud-Based Storage
Now, organizations have at their disposal the opportunity to deploy storage that exists outside the organization and in the various data centers of cloud providers.  Of course, this storage is still the traditional kind of storage used by regular enterprises, but when used in a cloud environment, it's presented a bit differently and there are technology challenges and new cost scenarios that must be studied.  Cloud-based storage can be a good fit for backup and archival purposes, but is also emerging as a potential fit for file-based scenarios.  In addition, cloud storage can be, for example, a useful place to store large data sets for analysis using a cloud provider's very scalable compute architecture.  Once the number crunching is done, you can just download the results.  It's another way that cloud can be used to meet new business needs.

First, the good: Using the cloud for storage provides organizations with the flexibility to pay for only what storage is required and no more.  After all, why pay for 20 TB of storage today when you only need 12 TB?  Further, from a pure scale perspective, cloud storage is practically infinite.  You can just add more capacity as you need it.  You also have the opportunity to spread data across multiple zones, adding fault tolerance that isn't always feasible with on-premises storage.

However, the economics inherent in cloud storage can often scare away potential customers.  First, as mentioned earlier, cloud-based storage isn't sufficient when low latency is required.  However, that's only assuming that the latency-sensitive apps reside in your data center.  If they happen to reside "near" your cloud provider, latency might be acceptable.

On the economic front, depending on your provider, you may encounter a wide variety of charges that make you wonder whether or not cloud is a good solution for storage.  These charges include:

• Cost per GB of storage: This is generally dependent on how much storage you use -- the more you use, the lower the per-GB cost -- and the quality of the storage.  If you want standard storage, you will pay one rate.  If you're willing to risk less redundancy, you can get a lower rate.  This rate may also be dependent on the kind of storage -- solid state or hard disk -- that you're using.
• Data transfer:  With cloud providers, you pay for what you use, and this includes the storage network.  You pay for the amount of data that you transfer in and out of the cloud provider.  Some providers, such as Amazon, don't charge for you to push data into their S3 service, but do charge you to transfer it back out.
• Request pricing:  Each time you request data, there is a small charge incurred.

These costs can add up to big time numbers if you don't keep an eye on things.  It's important to note that storage in the cloud is not cheap.

While not a comprehensive analysis, this column explained some of the pros and cons of on-premises vs. cloud-based storage in order to provide you with a bit of additional insight into how these two kinds of storage operate and in what situations they make sense.