Demystifying cloud storage

by Sharon Lobo    Mar 30, 2010

Cloud storage is not a disk array that you own, lease, or manage neither is it a virtual logical unit number (LUN) from a larger disk array. It is in fact it is offered via an application programming interface (API) through which you can send and receive data without having to actively manage the storage.

Cloud storage is offered by many vendors in different packages. Businesses using cloud storage services need not worry about RAID levels, parity, disk swaps, space management, replication, error condition monitoring and reporting etc.

Through service level agreements (SLAs), vendors can receive and store the data you have sent to them, and retrieve it when you request. As long as the vendor meets the SLAs to which you have agreed, how or where they store the data is up to the cloud vendor.

Pricing
In a cloud storage model, your monthly fee is based only on the amount of actual data present at the provider s site (and sometimes also how many GBs you transfer to/from their site). It supports burst pricing, which means if you need to store 20TB this month but only 3TB next month, you can do that with no configuration changes, or anything like that. All you do is pay for 17 less Terabytes next month than you did this month.

Appropriate data type
In cloud storage the data is accessed over the Internet, thereby it will not offer the same performance characteristics of local storage. Therefore cloud storage would not be appropriate for large data sets that are constantly sent to and read from storage, such as databases. As a result cloud storage is appropriate for backups and persistent data . Backup systems are well known to everyone; and, persistent data is that data that you have to keep around (often for legal reasons) but would not actively manage.

Businesses benefits
When it comes to backup, SMBs are the first to benefit from cloud storage, as they do not create the amount of backups that enterprises create, so there are few bandwidth concerns for backups or restores.

In case of enterprises, cloud storage is perhaps not the best place to store backups for very large data centers. However, small remote sites of enterprises can use cloud storage for backup.

Speaking of persistent data, any business that identifies a significant portion of its storage being wasted due to such data can opt for cloud storage.

Bandwidth considerations
Bandwidth requirements of moving your data to the cloud must be examined along with the costs of meeting those requirements. However, depending on the application, additional bandwidth may not be needed. For instance if your company has almost no need for bandwidth at night, you can use all available bandwidth to send backups or persistent data to the cloud at no additional cost.

Inhibitors to adoption
The first objection that many people have is cost. They look at cloud storage costs that range from $0.15/GB to $0.75/GB per month and think they could do it much cheaper than that. However, rarely is that the case and any good cloud storage provider can help you do a full TCO analysis of doing it yourself versus storing the data in the cloud. These TCO analysis models take into consideration a number of important factors. Let us consider a few.

Data protection: If you have 1GB of usable protected data, you will need close to 3GB of actual disk (or more) even if you use the least expensive RAID levels (parity-based protection, not mirroring).
Power and cooling: These are the primary cost factors in many data centers. Electricity is required to run disk drives and cool the heat generated by them.
Technical refreshes: If you are managing your own storage, you have to bear the costs of upgrading the equipments, migrating the data from one platform to other and also the day-to-day monitoring and management of the system.
Engineering and planning: To design the next generation storage system, you would need experts to evaluate all the options available to your environment and to then work with prospective vendors. The cost of these infrastructure engineering people often goes ignored when considering the costs of managing your own storage.

Security and reliability still a concern

The next big objection that people have to overcome when considering cloud storage is that of security. Therefore it is well advised to retain the services of a security expert when evaluating cloud storage providers. Make sure that this expert is completely happy with all of the answers with any cloud storage provider you are considering.

In case of reliability, examine the history of the reliability of any company that you are considering. Remember again that just because some cloud storage providers have had major outages even data loss does not mean that all cloud storage is unreliable or unsafe.

This article has been written with inputs from CommVault Systems, a US based company specializing in data and storage management software.