Curbing NAS data growth via a combination of storage quotas, IT chargeback mechanisms

In the data storage world, sometimes you learn the right way of doing something by watching someone else do it the wrong way. Case in point: The support team for one client of mine, a large financial institution, was required to do on-call rotation -- that is, handle support calls after normal work hours, on a rotating basis. These support calls would sometimes come in the middle of the night. Out of curiosity, I asked members of the support team what the most frequent trigger for a middle-of-the-night wakeup call was, related to their NAS arrays. The answer: file system

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storage quotas that were full. To fix the file system problem, members of the support team would simply increase the storage quota. But doesn't that defeat the purpose of a quota? Rather than simply increasing the storage quota (thereby losing an opportunity to contain data growth), utilizing quotas in conjunction with an IT chargeback model is the only meaningful way to curtail data growth without impacting all users on the same NAS volume.

Storage quotas give the organization a way to limit how much data is being used by a department, and the IT chargeback mechanism ensures that the specific departments pay for those services.

An analogy to the storage quota/chargeback model is a storage facility with multiple tenants in one physical space. If the tenant wants more storage, he needs to either pay for that extra space or better manage the space that is allocated to him. The same is true of unstructured data on a NAS volume. If you have proper storage quota and IT chargeback mechanisms in place, users cannot simply ask for space. They either have to manage the space they have much better or go to their manager and justify why they need to buy more storage space; since the business unit manager's capital expense budget carries the cost of the extra space, he has a vested interest in capping employees' use of space. And, your customer's storage administrators wouldn't have to get involved in a discussion about whether a quota needs to be increased.

It makes sense to get the business folks involved, since data growth contributes to costs to the business. Increased data creates larger snapshots and replicated volumes, and it requires more tapes and longer backup times. To help control that growth, policies around data usage need to be set at the top. Quotas and chargeback could help your customers get a handle on their company's storage growth.

But, it's not a simple process to enable IT chargeback. It requires organizational changes as well as buy-in and cooperation from multiple departments within a company: management, finance/accounting and IT. While there are software tools that help implement storage chargeback processes, they're only part of the solution. Assuming company management endorses the IT chargeback policy, finance/accounting need to come up a means of charging internal departments, and the policy needs to clearly define what the charge includes (for instance, the storage resources themselves, as well as real estate costs of the data center, electricity/heating/cooling, and replication infrastructure for data that's replicated to a secondary array).

As a storage reseller, integrator or consultant, you can't directly influence the entire process of setting up a customer for a chargeback mechanism, but you can help them build the case for it. It's a benefit both for your IT customers and to the company they work for, since it can help them save money by curbing data growth. And, it represents the kind of advocacy that helps establish or maintain your status as a trusted advisor.

About the author

Seiji Shintaku is an independent consultant and has been focused on Post Sales support and delivery for RBS, Merrill Lynch, Credit Suisse First Boston, IBM and Morgan Stanley. Seiji can be contacted via email or LinkedIn.

This was first published in March 2010

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