What is a Storage Controller? This is another in our series of ongoing chalk talk articles on various subjects impacting the storage industry today we're going to focus on George controllers this subject has become a recently a top read subject on our website we have an article on our site called what is the storage controller that has grown through organic search and so clearly it's something that people want a lot of information on so let's talk about that so first let's talk about what a storage controller is and where it goes so from a positioning standpoint you can think of a storage controller basically as a computer that goes inside a storage array okay and so usually a classic storage system has a dual controller system so these are basically typically two CPU modules they can be multi-core and things like that and then there's a series of disk shelves that attach into that the CPU does or the controller does all kinds of different things in the early days of raid and things like that and and external volumes primarily what it did is some level of volume management and also typically raid rate as we've talked about is a form of data protection of some sort to protect your in case of a drive failure there's different raid levels that most people are familiar with raid 5 and raid 6 being probably the most popular nowadays but this controller unit and I think one of the reasons that this article has risen in popularity now does a lot more things than just volume management and raid one of the big features that everybody always asks for is snapshots and then they also are now doing things like thin provisioning well all of these different functions that we asked the storage controller to do take essentially CPU cycles right so we're asking a CPU to do more or work and so what happens as these CPUs have to get more powerful in addition the there's an IO path that goes between this controller and these dis shelves the more discharge you have the more IO there is the heart of the CPU is going to work just doing volume management and raid so the combination is all of a sudden we're starting to see for really the first time storage controllers not be powerful enough to drive the number of drives that people need and to do the type of functions that they require a great example is a new function that is say came out in the last two years or so is to automated tearing and what that is let's say we had a shelf of SSD and a shelf of HDD and maybe a shelf of high capacity Nearline HD DS and we'd want to what Auto tiering does is automatically move data at a block level between these tiers except those arrows I just drew aren't exactly accurate because really what happens is when data is being processed it has to travel up to the CPU be analyzed and then put back down on the correct here so once again we're asking that Refurbished controller unit to work harder. So what's the impact of this is as I said the CPUs are now working harder and harder and we need more and more power there so when a system runs out of CPU power what you eggs essentially have to do is what most people do is upgrade and buy a whole new system they either put an other new system here or they just replace this one put a new one in so when you're doing a storage refresh many times that's what's driving it but this is now led to changes in the industry where controllers are going in different places and there's probably two big initiatives that we see that impact that first is the scale out storage type of method right and so instead of one big control of what we have at scale out storage is a smaller node and inside that node is a series of disk drive so node can also be essentially a server so there B drives inside there and then to add more power we add another node and more disk drives and then another node and more disk drives and so essentially it scales out right the value and then the volumes essentially artists so if you had a file the file writes across all of these nodes so all the processors that I have drawn there are involved in writing data reading data analyzing data all those different functions that we were talking about the other big initiative is either software-defined storage or hyper scale data centers where essentially we've got a virtualization cluster and in that cluster we've got obviously VMs running
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