The old pain in the DAS !!
Is it me, or are others in the field seeing more and more companies being pushed to look at DAS solutions for their application environments? It strikes me as pretty interesting. I’m sure mostly it’s positioned around reducing the overall cost of the solution, but I also think it has a lot to do with assuring predictability around performance that you can expect when not having to fight for IOPS among other applications. In fact, Devin Ganger did a great blog post around this very subject in regards to Exchange 2010. It was a pretty cool read. I left a comment on his site, it pretty much matches (some may call it plagiarizing myself ) my discussion here but I’ve had some time to expand a little more. As such, here are my thoughts on my own site
Let’s take a look back 10 years or so. DAS solutions at the time signified low cost, low-to moderate performance and basic RAID-enabled reliability, administration time overhead, downtime for any required modification, as well as an inability to scale. Pick any 5 of those 6 and I think most of us can agree on it. Not to mention the DAS solution was missing key features that the applications vendors didn’t include like full block copies, replication, deduplication, etc. Back then we spent a lot of time educating people on the benefits of SAN over DAS. We touted the ability to put all your storage eggs in one highly reliable, networked, very redundant, easy-to-replicate-to-a-DR site-solution, which could be shared amongst many servers, to gain utilization efficiency. We talked about cool features like “Boot from SAN” as well as full block Snapshots, replicating your data around the world and the only real way to do that was via a Storage array with those features.
Fast forward to today and the storage array controllers are not only doing RAID and Cache protection (which is super important), they also doing thin provisioning, CDP, replication, dedupe (in some cases), snapshots (full copy and COW or ROW), multi-tier scheduled migration, CIFS, NFS, FC, iSCSI, FCoE, etc etc. It’s getting to the point that performance predictability is pretty much going away not to mention, it takes a spreadsheet to understand the licensing that goes along with these features. Reliability of the code, and mixing of different technologies (1GB, 2GB, 4GB, FC Drive bays, SAS connections, SATA connections, JBODs, SBODs, loops) as well as all the various “plumbing” connectivity options most arrays offer today is not making it any more stable. 2TB drive rebuild times are a great example of adding even more for controllers to handle. Not to mention, the fundamental building block of a Storage array is data protection. Rob Peglar over at the Xiotech blog did a really great job of describing “Controller Feature Creep”. If you haven’t read it, you should. Also, David Black over at “The Black Liszt” discussed “Mainframes and Storage Blades” he’s got a really cool “back to the future” discussion.
Today it appears that application and OS/hypervisor vendors have caught up with all the issues we positioned against just years ago. Exchange 2010 is a great example of this. VSphere is another one. Many application vendors now have native deduplication and compression built into their file systems, COW snapshots are a no-brainer, and replication can be done natively by the app which gives some really unique DR capabilities. Not to mention, some applications support the ability to migrate data from Tier 1, to Tier 2 and Tier 3 based not only on a single “last touched” attribute, but also on file attributes like content (.PDF, .MP3), importance, duration, deletion policy and everything else without caring about the backend storage or what brand it is. We are seeing major database vendors support controlling all aspects of the volumes on which logs, tablespaces, redo/undo, temporary space, etc. are held. Just carve up 10TB’s and assign it to the application and it will take care of thin provisioning and all sorts of other ‘cool’ features.
At the end of the day the “pain in the DAS” that we knew and loved to compete against is being replaced with “Intelligent DAS” and application aware storage capabilities. All this gives the end user a unique ability to make some pretty interesting choices. They can continue down the path with the typical storage array controller route, or they can identify opportunities that leverage native abilities in the application and “Intelligent DAS” solutions on the market today to vastly lower their total cost of ownership. The question the end user needs to ask is, ‘What functionality is already included in the application/operating system I’m running?’ vs. ‘What do I need my storage system to provide because my application doesn’t have this feature?’ At the end of the day, it’s Win-Win for the consumer, as well as a really cool place to be in the industry. Like I’ve said in my “Cool things Commvault is doing with REST”, when you couple Intelligent DAS and application aware storage with a RESTful open standards interface, it really starts to open up some cool things. 2010 is going to be an exciting year for Storage. Commvault has already started this parade so now its all about “who’s next”.
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