This is a series of posts covering the subject of Storage Management. Previous posts:
As discussed previously, the Service Catalogue is a key component of delivering storage as a service. In this post, I’ll explore some thoughts on developing a Service Catalogue and how its abstraction from technology allows the delivery of a more efficient operation.
What’s in a Name?
- It should be abstracted from technology.
- It should provide service metrics – explaining what you get for your money.
- It should be able to scale up or down to meet customers requirements.
- It should provide charging information based on simple billable units.
Comparison with Other Industries
- It should be abstract from Technology. This rings true for the delivery of say, electricity to a domestic dwelling. In the UK, everyone expects to receive 240V at 50Hz as a standard. Changing to another supplier doesn’t require a change in electricity standard; the process of electricity generation doesn’t affect the end delivery, whether it is generated from wind, wave, nuclear or coal.
- It should provide service metrics. Whether explicitly written into a contract or not, I think most electricity users would expect their service to be available on a 24×7 basis. In addition, the supply should be guaranteed to remain within certain tolerances – e.g. 240V±10% and 50Hz±1% for example. Deviation outside of these standards would have a seriously adverse effect on equipment using the supply.
- It should scale. Unless you’re a commercial user, most electricity companies would expect to be able to increase and decrease their electricity consumption without consideration of how that supply was provided and without contacting the provider. In fact in the UK the National Grid are responsible for monitoring demand and bringing supply in and out of use to match requirements. This is all part of the service and therefore included in the cost of supply.
- It should consist of Billable Units. Check your electricity bill; you’ll find your charge is based on a price per kWh, a standard unit of measurement of power. Your charges are directly related to your consumption and not to how the power was generated. It’s worth noting that some providers will offer multiple tariffs, for example providing cheaper electricity at night or tying consumption into green issues. These tariffs are analagous to storage tiers.
Building a Service Catalogue
- Look to include functional requirements (availability, response times).
- Look for cost & service differentiation. Some organisations implement many different tiers of storage or product offerings. Implementing multiple tiers can become expensive and if they’re not all utilsed efficiently, then the potential cost benefit is lost. Implementing multiple tiers offers the ability to reduce costs by placing less active or less demanding data on cheaper resources.
- Look to drive behaviour; implement services that penalise lack of adherence to standards and so on, but reward forward planning and utilising forecasted resources.
A Basic Template
- Gold - Availability – 99.999%; Response time: <10ms on 99.9% of I/Os sampled over a 5 minute period. Connectivity – FC – $10/GB/Month
- Silver - Availability – 99.999%: reponse time <15ms on 99.9% of I/Os sampled over a 5 minute period – conncetiivty – FC – $5/GB/month
- Bronze – Availability 99.9%; reponse time < 20ms – connectivity = iSCSI – $2/GB/month
- Local replication. Add a local replica for an additional tier price per month (gold replica for $10/month)
- Remote replication. Add a remote replica for the cost of the replica plus 10% (e.g total cost per GB for gold is 22$/GB/month