Taking a Quick Look to Software Defined Storage (SDS) – Part I


Do not be afraid; meet this new (or not so new) player in town: Software Defined Storage (SDS). Moreover, why is it important for you to know about its existence? Why should you start considering evaluating it in your solutions deployed within your organizations or customers? Let us take a quick look into the technology, what represents, and the main benefits.

Before getting into Software Defined Storage, let us recap about the storage definitions we had before SDS:

  • DAS: Direct-attach storage, like the ones you have on your notebook, desktop or tablet, hard drives attached to a mainboard. No complications here, DAS types differ from each other on the way they are connected to that mainboard.
  • SAN: Storage Area Networks also connected to the hosts (mainly servers) but via a backplane using adapters and cables. These type of connections vary from Fiber Channel, iSCSI (which is SCSI, Small Computer Systems Interface, but over internet) and Serial Attached SCSI or SAS. SANs still are by far the main storage deployment for servers we can find in organizations.
  • NAS: Network Attached Storage, is what we commonly understand for “file servers”. Servers with storage attached (which can be DAS, SAN or SDS) prepared for file sharing. Accessing a NAS it is not performed as DAS or SAN work, using SCSI protocol, but using a network file system like SMB from Microsoft, which works over TCP/IP.


So, when actually RAID technology starts to play?

RAID (Redundant Array of Independent Disks) appeared a long time ago as an answer to achieve some protection and improvement within the data we stored in the hard drives, showing as a single drive a combination of several disks.

RAIDs are configured using software installed in a server or within an array controller. Some people call the latter “hardware arranged RAID”, but it is software nevertheless installed on an array controller.

This software dependent storage called RAID introduced improvement on how we considered storage, but with a large complexity costs. Specialized hardware is needed to achieve RAID, interconnections and arrays prepared (vendors specific); software to integrate with all those components. Each components has to be compatible with each other, if any problem appears, the data within that storage could not be accessible.

Outlining Software Defined Storage

SDS introduced the concept of separating completely the hardware from the software that managed this storage. This idea of decoupling the hardware from the solution, easily relates with the virtualization concept: SDS does for storage what virtualization does to servers, which is why we also call SDS as virtual SANs.

There are varies definition about experts that define storage virtualization as not the same concept as Software Defined Storage. We will tackle the differences along the way in the series of posts I have prepared.

SDS is no other than a software layer handling the data access to hardware, but we can even say, “That’s exactly what RAID technology does!” and we will be somehow right. However, RAID will use software to transform several disks into one, that is just one characteristic we can achieve from SDS. Using Software Defined Storage, we can define different features, ways of access the data, and policies like QoS, integrate several different components (hardware and software) which is usually not possible with RAID, and so on.


Image used from http://headintotheclouds.com

Regarding the technologies and vendors we can find offering SDS solutions, there will be differences as well. StarWind concepts about SDS differs from what you VMware has to offer; and Microsoft concept is different about VMware’s conception. We will take a closer look also of those in the following articles.

Main Benefits about Using SDS

Before getting to know the alternatives, vendors and technologies within SDS we can find, let us take a review about the main benefits on using Software Defined Storage for our solutions:

  • Decoupling software from hardware gives you more possibilities when handling your storage/s solutions: As mentioned before, using different disks as one is just one section in SDS, we can define different ways on how to access data, policies applying to different workloads, hypervisors; automation possibilities; and several other features.
  • Heterogeneous storage is possible: Related to the benefit mentioned above, adding a software layer also allows us to use different type of storage, different type of disks, arrays and even hardware vendors to manipulate the same SDS we define. You will no longer depend on a specific vendor when considering to improve or expand your storage solution.
  • Control performance and capacity: Much easier to control on how the storage is used by the solutions hosted; managing the performance our workloads can access depending on our definitions; dynamically expanding capacity and performance as our systems needs it is one of the main benefits within Software Defined Storage.
  • SDS solutions can provide the possibility to reduce storage costs immensely: Software Defined Storage concept, depending on the vendor you select, work on commodity and inexpensive hardware. TCO (Total Cost of Ownership) is greatly reduced since we reduce the cost not only for the hardware, but also about maintenance and operations.

As we can see, SDS represents the dynamic solutions our customers require daily, in a market where 24x7x365 represent no longer as an “added value” but a necessity. Without Software Defined Storage, the solutions we implement in our datacenter will continue maintaining dependencies and will be restricted on scaling out.

In the following articles, we will review on the alternatives we have with SDS, vendors, comparing solutions and so on.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s