The problem however is how do you optimize your capacity? This is storage that has been hard assigned to a server but has not yet been consumed. It's that "little extra" you give to each server to keep from having to continuously provision more storage to that server. Thin provisioning has established itself as the ideal way to free up this captive capacity. Be careful though, thin provisioning is its most effective on its first day and on net new data. As data is deleted from the volume the system does not reclaim that capacity. Modern thin provisioning systems as we discussed in our white paper "Thin Provisioning Basics" have evolved to be able to overcome this weakness, reclamation can now be done with certain file systems and on second generation thin provisioning systems.
If you are like many data centers only 25% to 35% of your actual capacity is actually storing real data. If for some reason you added one of the above data optimization technologies then it may be an even lower percentage. As you know you simply can't turn drive shelves off. Most storage systems are designed to write data vertically across shelves for increased redundancy. There is typically no free shelf of storage.
These advanced thin provisioning systems are ideal when you are refreshing your legacy storage system, but what if you are not able to do so? If you have a legacy storage system with low utilization rates but no thin provisioning type of features, is there a downside? After all you have more than likely already bought and paid for the equipment. Why buy something new to get one capability?
There are downsides to not being able to increase utilization. First this wasted capacity may cause you to buy more storage capacity sooner than you should need to. Second you are paying to power and cool that additional capacity. Third that capacity is taking up additional floor space in your data center. Floor space that you probably need for something else. If you are anywhere close to the 25% utilization statistic, that means you can reduce purchases, power and cooling and floor space by as much as 75%. That alone may justify a sooner than planned storage refresh.
Over the next several entries we will cover how to get more utilization out of what you have, if your going to refresh what to look for and how to manually re-optimize a storage system to be able to power down parts of it.
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George Crump is lead analyst of Storage Switzerland, an IT analyst firm focused on the storage and virtualization segments. Find Storage Switzerland's disclosure statement here.