Cloud storage service-level agreements (SLAs) specify uptime guarantees but not data availability

Today's service-level agreements (SLAs) for cloud storage capacity typically provide guarantees in terms of uptime but specify little in terms of data availability or data protection. Corporate IT shops do, however, have some ability to negotiate additional provisions into their SLAs for cloud backup or cloud archive, according to Terri McClure, a senior analyst at Enterprise Strategy Group in Milford, Mass.

McClure spoke recently with SearchStorage.com about what end users can expect to find in their cloud storage SLAs. Learn about cloud storage SLAs in this FAQ interview or download a podcast of the Q&A.

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Cloud storage SLAs assure uptime, not data availability
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SearchStorage.com: Can you provide a very brief definition of cloud storage, and what is typically covered in a cloud storage service provider's SLA?

McClure: For the purposes of this discussion, I'm referring to storage service providers that offer bulk capacity services online, like Nirvanix, Rackspace and Amazon's S3 [Simple Storage Service]. Most of these storage service providers have very well-defined service levels that can be easily found on their Web sites. Typical cloud storage SLAs cover what to expect for service levels and what users are entitled to for recourse. So within the details of the SLAs, it's pretty common to see guarantees that the service will be available 99.9% of the time. These SLAs also cover what's defined as service availability -- in other words, how long a read request can take to be serviced before it's considered outside of compliance with the SLA, how many retries are allowed and things like that. They also define what sort of recourse users have if they don't meet the 99.9% uptime guarantee. And most of them offer some sort of tiered service credit plan where users get, for example, a 10% credit if the service is available only for 99% to 99.9% availability, and then higher credits the lower the actual service levels delivered are.

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SearchStorage.com: What are the major shortcomings that companies need to watch out for in their cloud storage provider's SLAs?

McClure: These agreements sound pretty good as far as service availability goes. After all, 99.9% uptime sounds impressive, but it's nine hours a year of downtime. So once critical business applications are considered, many users have very little tolerance for downtime before suffering a major adverse business impact or loss of revenue. In this light, nine hours can be a lot.

With some storage service providers, you can pay a little extra and get geographically dispersed copies of data, and that can help. But the challenge is that remote copy does not protect you just from the most common driver for recovery requests, and that's accidental deletions and software bugs that cause data corruption. Remote mirroring just ensures the bug is replicated and the data is deleted in multiple places. So backup or point-in-time copy is, for the most part, something the subscriber still needs to plan more and staff. This lack of integrated data protection needs to be a core consideration when deciding what can be stored in the public cloud.

SearchStorage.com: Do corporate users have much ability to negotiate extra provisions into their cloud storage SLAs?

McClure: The business model for most cloud storage providers is based on providing a generic set of services and selling bulk storage in volume, and key to that is keeping operating expenses and SG&A [selling, general and administrative] costs very low. So, most don't provide that ability. Flexibility in SLAs is offered, though, if users are contracting an external provider to build maybe a private managed cloud at a higher cost than subscribing to the public cloud service, but not really with these generic cloud offerings that we're discussing today.

SearchStorage.com: What's the main difference between SLAs for cloud storage versus SLAs for cloud backup or cloud archive?

McClure: This is where the ability to negotiate data protection levels comes in. So, this is where you can start to customize your SLAs. Users can define retention policies, number of copies that need to be retained, where they need to be stored. Most of the things they define for in-house backup and archive can be negotiated in the SLA when they're buying storage backup or cloud archive services.

SearchStorage.com: Would you advise a corporate user to enlist an attorney in the process of negotiating an SLA?

McClure: If you're negotiating with a service provider to provide, let's say, private cloud services as a managed service, it's always good to ensure your business is not exposed and all the T's are crossed and I's are dotted. But, for the public cloud, you might want to have your corporate counsel look at the documents so you know exactly what you're getting into, and you fully understand both you and your service provider's liabilities. But it would be for that purpose only. So yes, I think it's important to have the lawyer look it over so you know what you're in for.

SearchStorage.com: In closing, what's the primary piece of advice you'd like to leave with end users with respect to cloud storage SLAs?

McClure: It's really important to read the fine print. We've been generalizing here, but really, not all SLAs are the same. I know of one vendor SLA, for example, that offers 99.9% uptime. It sounds pretty good. But they don't count downtime unless the client can't access applications for more than 10 minutes. A nine-minute outage is not considered downtime for them in their SLA. So in that case, in the event of downtime, all the client is entitled to are service credits with that provider. So you don't have a lot of recourse there, but you could have a lot of downtime and still be within the SLA.

Some services are more granular, but the overall point is that cloud storage services were really designed as consumer-grade solutions that are being extended to businesses. Cloud services are a fast and inexpensive way to build an IT infrastructure without any capital outlay or in-house infrastructure management capabilities. But you get what you pay for, and the attractive 15-cents-a-month fee is for basic services only. For each extra copy of data or improved bandwidth for backup, it can push the price up very quickly. So I expect some solutions, like local gateway types of solutions, to start coming into the market this year to help with some of these issues. But until then, users need to fully understand what they're getting into when moving data into the cloud.

For more on cloud storage:

1. Find out why the evolving cloud storage market has users weighing their enterprise data storage options

2. Discover why external cloud storage appeals to smaller firms, but large enterprises remain cautious

3. We explain how internal private cloud storage makes its way into larger enterprises

4. Read why not everyone thinks the future is bright for clouds

This was first published in February 2010