Outsourced infrastructure provider Savvis has selected arrays from Compellent Technologies to power a new cloud storage service that will see up to 120 TB of disk space implemented at each of three data centres in the UK and US. If the Compellent implementation is a success for the Savvis cloud offering at its 28 data centres worldwide, it will result in approximately 3.3 petabytes (PB) of Compellent storage installed.
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The service provider said it chose Compellent because of its ability to provide automated tiered storage -- something its incumbent storage provider, 3PAR, was unable to do. Automated tiering was necessary for Savvis to provide differing service levels to customers, as well as to provide optimum use of energy on the most appropriate cost of disk. 3PAR is not expected to incorporate automated tiering until next year. But 3PAR products will continue to be used for Savvis's Dedicated and Open Cloud products.
We went to 3PAR first, but it was a timing issue that saw us go with Compellent. 3PAR couldn't offer the tiering that Compellent could.
technical VP for storage architecture, Savvis
The implementation is the first phase in Savvis' Project Spirit, which is its planned roll out of a virtual data centre product based on VMware-based virtual servers and Compellent storage.
Savvis expects to launch the beta version of Project Spirit with multitiered quality of service capabilities later this year.
Savvis will install between three and five so-called Storage Pods of 120 TB of capacity at two US data centres and one in London. Each will consist of dual controller Compellent Storage Center arrays with three tiers of disk – 15,000 rpm Fibre Channel (FC), 10,000 rpm FC and SATA.
Each tier is further subdivided between RAID 1 mirrored capacity and RAID 5 parity-based data protection. RAID 1 offers quicker IO performance than RAID 5, which is slower because of the need to make parity calculations.
The three main tiers by disk type parallel Savvis' service offerings to its customers: Enterprise, Balanced and Essential.
Todd Loeppke, technical vice president for storage architecture at Savvis, described the process by which data is tiered.
"New writes go to the outside of the platter and onto RAID 1," he said. "Once a night, a job runs and looks at the blocks and data use patterns. Newly written blocks which have gone to RAID 1 are moved to RAID 5 and also, depending on usage and service level, go to tiers 2 or 3. All this is done automatically according to profiles set up to configure the system."
Compellent's automated tiering beats out incumbent 3PAR
Loeppke explained that Project Spirit requires a platform that addresses Information Lifecycle Management (ILM) at a more granular level than the typical logical unit number (LUN) approach. This enables the firm to drive out cost for its customers while maintaining enterprise features, he said. "Compellent's automated block-level ILM provides the 'knobs' Savvis needs so that we can provide multitiered quality of service as it relates to storage," he said.
"We went to 3PAR first, but it was a timing issue that saw us go with Compellent," Loeppke said. "3PAR couldn't offer the tiering that Compellent could. They could move data at the LUN level but didn't have the capability to move it with the same granularity. Compellent tracks data at the block level."
Compellent included automated movement of data blocks between tiers as a feature of its Storage Center subsystems some time ago. EMC plans to introduce it to its high-end Symmetrix arrays later this year. 3PAR has been working on its 3PAR Adaptive Provisioning technology for some time in which individual storage blocks are moved according to policy between storage tiers, but is not expected to include it in products until mid-2010.
The Compellent automated tiering enables the Savvis to extend its choice of service grades into storage functions by offering customers choices of performance, cost and data protection. Automated tiering also increases performance and lowers cost as critical data is reserved for the fastest storage, while data that is less performance-sensitive is automatically assigned to slower, less-expensive storage.
Is there anything Loeppke thinks Compellent could do better? "I'd like to see more ways to access data, a better NAS product and SOAP/REST Web API access."