At a recent event we were fortunate to have a Dell customer speaking as an advocate for the Dell Compellent Storage solution. He spoke in great detail about the process of moving from a traditional storage solution to Dell Compellent. He made some great points, but the one that struck me most was the discovery they made when they started the automated tiering on the system. First, let me give you some background on tiering. Within the storage system you typically have multiple types of disk. These range from high-end, and expensive, fast disks to slower and therefore cheaper disks. The strategy of tiering is that you do not want to have data on fast expensive disks if it is rarely accessed. Similarly, if data is accessed regularly by many people then you want to place this data on the best most accessible disks. The target is that all data is accessible at an appropriate speed for the user base. The real benefit to the customer is that they do not have to estimate the amount of fast disks they need to meet their user base needs. The tiering process on Compellent not only tells them where the data should be, but also moves the data to that appropriate disk.
So back to our customer, he gave details on how they set the system up to analyse the data once a week for the purpose of tiering. After the first week they were very surprised by the results. These results were borne out week after week and the simple fact was they had completed misunderstood the lifecycle of the data within their systems. Data that they believed to be critical and needed to be on the first tier for fast access was never accessed after creation and other data that they attached little of no importance to and believed should be slow, cheap disks was in fact accessed regularly by multiple users. It is very easy for system administrators to be stuck in the frame of mind that requires them to think solely in terms of megabytes, terabytes and IOPS and lose sight of why they are providing the system and more importantly how it is used on a day to day basis.
Let me give you a hypothetical example. A patient comes to a hospital for a MRI scan. What is the most important data, the actual picture of the MRI scan or the patient’s address? Obviously the MRI scan is critically important to the diagnosis of whatever health issue they may be dealing with and the patient’s address is very much secondary. After all they have the patients name and some form of reference number. Anyone looking at the system would be able to make an objective decision based on this information and decide where the best place to keep this data. But they could be wrong and this is what the tiering process would highlight.
The MRI scan is stored once and accessed by the MRI technician and sent to doctor or consultant dealing directly with the patient. This results in the data being accessed twice. There may be a follow up some months after that or if the patient is fortunate then the scan may never be needed again. However, almost every time with each access of the patient’s records, they validate they are looking at the right patient by confirming the address. So everyone from the consultant and the MRI technician to the hospital reception and ultimately the billing department look at the address.
In terms of the system the address is far more important than the actual scan. It is accessed by far more people and more times than the scan. Important is of course the wrong word and we have to start thinking about data in different terms. This is critical for system administrators to understand their data and more importantly to be able to articulate this to their own internal customers. You can imagine the conversation between the system administrator and the doctor where they tell them the MRI scan is not “important”.
When analysing data, the system has no natural bias or prejudice. Unlike people who will make subjective decisions based on their own “feel” for what they believe to be right. The Compellent solution provides a mechanism for organisations to get to grips with lifecycle of their data. The results may surprise many, except those that have been using Compellent for some time. It is not budgetary constraints or penny pinching that drives post installation sales on Compellent. It is simple, unbiased analysis that results in over 80% of sales on existing systems being slower, cheaper disks.