Virtualization Putting DAS Back in Play

Arthur Cole

What's old is now new and what's new is -- well, I don't remember how the rest goes, but the first part of the saying is very appropriate to direct-attached storage these days.


It seems that more and more enterprises are coming to the realization that virtualization and SANs, while offering a number of advantages, particularly to large organizations, is a pain in the patukus to manage. So a number of people have been reverting to good ol' DAS to simplify things a bit.


Paul Shread over at Enterprise IT Planet took a look at this trend a few days ago, noting that, if done right, direct-attached SAS designs can even improve efficiency and flexibility in many environments. He notes that HP recently unveiled a new SAS storage option for the BladeSystem line capable of scaling up to 192 TB across as many as 32 blades. The package consists of the StorageWorks 3 Gbps BL SAS switch, the P700m Smart Array Controller and the MSA2000sa array.


The goal, according to Lee Johns, HP's director of marketing for entry-level storage, quoted here on Infostor, is to offer the advantages of shared storage without the cost and complexity of a full-fledged SAN. Each MSA module has one controller and three disk trays that hold up to 12 1 TB SATA drives and can service all the blades in a C7000 and C3000 enclosure.


For those who can afford it, though, a good management stack can make the complexities of a SAN worthwhile, according to George Crump of Storage Switzerland. Once you're on the virtualization fast track, a key requirement is the ability to see the interaction between storage, VMs and their physical hosts, allowing you to choose the most available storage, processing and I/O resources. Sure, it's complicated, but at least you know you're getting the maximum use out of your enterprise infrastructure.


Nonetheless, low-end customers are calling for DAS, so it aims to please, says Mike Young, CEO of storage designer Sullego. The company recently unveiled a new DAS-friendly virtualization server, the ES100, for customers only looking for basic storage. As he says:

Today's DAS solutions are cheap, roughly sub-$2/Gbyte. But they also represent monolithic, fixed-featured investments. They don't back up. They don't replicate. They don't run virtual machines. And the list goes on. We wanted to provide a solution for our customers, priced as low as $1/Gbyte. And when they exhaust the capabilities of it, they can simply buy another and another. As their needs grow, these servers can be parallel-clustered to scale both capacity and performance.

As an old friend from my days covering video-production technology told me once:

You may have the most advanced technology in the world, but trying to get customers to buy something they don't want is like trying to push on a rope.

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Add Comment      Leave a comment on this blog post
Nov 29, 2008 4:16 PM imre imre  says:
With many today servers, you can attach 2 or more internas SAS RAID controler and there is a place in 4U or 5U case from 16 to 24 internal hot plug disks. So we can have 24TB SAS redundant storage(or more in some server cases). Today is also posible to buy cheaper 7200 SAS drives, but in many cases there is no need for 15k rpm, the internal architecture of server chipsets,I/O architecture, op systems, are limiting factors if server is doing something else than storage. Does not matter how many procs you have, the internal bandwith is the limiting factor. Also, to many marketing talk about virtualization in ANY case. Example, you have 20 servers with 20% mean usage, but several times weekly it goes to 80%(more than half of servers) or up. Randomly, of course.Is it case for VM? Yes, you can make expensive infrastructure, add several new servers with VM management and automatic dynamic load balancing between different hardware and VM. It works, but not in every case, and believe me, when there is a truoble, it is a BIG one. End very expensive, believe me, much more expensive than to use servers without virtualization in some situations. Just think, what, where, why, when,because it is not writen in white papers and customer satisfaction stories. Soltion for others is in most case not the best solution for us. And unfortunately, knowledge about optimization of today engineers is not up to date, it is much easier to spend $20k or $200k more :( Another question, is always blade server the best solution? But it is not for this article. Reply

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