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DAS vs. SAN cost debate revised with new cloud options

DAS is cheap, SAN is expensive, and neither quite meets the needs of most enterprise data centers. Storage admins can look to cloud and virtualization for a little relief.

Storage may not be cheap, but managing storage is truly expensive. The cost of managing data center storage can...

total up to four times as much as physical storage per gigabyte, according to research firm Gartner Inc.

The good news is data center administrators can lower their storage management costs in some unexpected ways.

The general belief in most modern data centers is that abandoning direct-attached storage (DAS) for a storage-area network (SAN) deployment will lower costs. But that is questionable.

Compare DAS vs. SAN on management: SAN is more expensive, and is far more complex to configure, manage and maintain than DAS. SANs require skilled administrators that are available at all times, whereas DAS is plug-and-go. A SAN administrator needs a higher level of education in deploying and managing storage than a DAS administrator. In many cases, DAS needs can be covered completely with hardware purchases.

Often, a company will use a mix of SAN equipment, so storage administrators must be educated on these different vendor implementations. Some companies hire several administrators to manage only one brand of storage within the mix.

Midsize companies often need more storage than DAS can efficiently provide, but on an IT budget that won't allow for the high investment in SAN and its associated ongoing costs.

Does that make managing storage cheaper with DAS vs. SAN? Absolutely. But cheaper doesn't mean DAS is better. When the business needs to extend its available storage, things get complicated. Without proper management, sooner or later, the amount of storage becomes overwhelming.

A data center can far more efficiently augment capacity in a SAN environment than in a DAS environment. Uncontrolled resources with lacking oversight will create storage-related problems and issues with the backups that ensure available capacity.

If it's just about static storage implementation and management, SAN is more expensive than DAS. But SAN affords you more flexibility, which may be worth the higher price.

DAS vs. SAN in the future

Midsize companies choosing DAS vs. SAN face some problems. DAS is inefficient, and SAN is relatively expensive. Midsize companies often need more storage than DAS can efficiently provide, but on an IT budget that won't allow for the high investment in SAN and its associated ongoing costs. These companies need to look outside the DAS/SAN dichotomy.  

Storage on demand in a cloud environment is one alternative: The company purchasing cloud storage doesn't have to manage it. While the cloud provider offloads administration, the disadvantage is that storage is no longer available in-house. This can cause problems for companies in various industries.

There is a lack of integration between the different SANs, ramping up the cost and complexity of managing storage. A company could standardize on one storage vendor to justify the upfront cost of SANs, but it's unlikely. With hardware from only one SAN vendor, administrators could streamline training and see the same management interfaces no matter what device is involved. In reality, however, equipment from different vendors already exists in the data center and it all has to be managed. Even when data centers standardize, vendors will release new versions with management updates that drift administrators back into that diversity conundrum.

The real answer to management costs might be software-defined storage, which abstracts the hardware from the management technologies. Today's software-defined storage ecosystem isn't very mature, and it isn't currently clear what the move involves. Vendors might put specific products, such as Inktank Storage's Ceph, Red Hat's GlusterFS, or even specific file systems in the software-defined storage category. Data center administrators need software-defined storage to manage various and diverse storage through one common interface.

Virtualization software could be the way forward to achieve this goal. Many current virtualization platforms integrate storage administration in the overall data center management suite. To share this common interface, each storage vendor must provide application programming interfaces that tie its products into the management tool. This approach will potentially slash storage management costs in the data center.

About the author:
Sander van Vugt is an independent trainer and consultant based in the Netherlands. He is an expert in Linux high availability, virtualization and performance. He has authored many books on Linux topics, including Beginning the Linux Command LineBeginning Ubuntu LTS Server Administration and Pro Ubuntu Server Administration.

This was last published in November 2014

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Is it an either-or? Can't you use SAN for the things SAN is good for, DAS for the things DAS is good for, and so on?
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