Dell Compellent storage Architectural advantages of Dell Compellent automated tiered storage By Bob Fine Tight integration, granularity, and system intelligence enable Dell Compellent™ storage area networks to build exceptional efficiency, automation, and scalability into sub-volume storage tiering on a fully virtualized infrastructure for the enterprise. n today’s data-driven world, an In comparison, the Dell Compellent optimized storage infrastructure Storage Center™ storage area network Smart, responsive, with intelligent data management (SAN) was engineered from the and well connected Iis at the heart of business process ground up to include automated tiered efficiency. Automated tiered storage storage with built-in data management offers an attractive way to help intelligence. Dell Compellent Storage manage rapid data growth and control Center SANs are based on the Dell™ costs. But organizations face a broad Fluid Data™ architecture, which is array of possibilities. By identifying designed to intelligently manage data key differentiators in the underlying throughout its life cycle—helping to architecture, IT decision makers ensure that information is available can effectively evaluate the cost when and where it is needed. This benefits of tiered storage systems and built-in intelligence enables Dell determine the approach that best suits Compellent Data Progression™ tiering their particular enterprise. software to integrate seamlessly with For example, many tiered Dell Compellent storage technologies storage offerings attempt to match to maximize storage performance, data with drive type, typically efficiency, and manageability. placing mission-critical data on A highly virtualized environment Dell Compellent Storage Center SANs high-performance drives and placing provides an excellent foundation provide the advanced automation less-valued data on high-capacity for automated storage tiering. The and built-in intelligence to help drives. However, tiering profiles intelligent storage architecture of the enterprises manage data flexibly, in this type of scenario are often Dell Compellent Storage Center SAN based on its business value. Fluid Data limited in scope and require manual is designed to enable true disk-level architecture also provides exceptional intervention to move and reformat storage virtualization by creating a application responsiveness by data from a disk group to a pooled single pool of storage resources that enabling integration across the configuration. Also, application spans all disks and RAID levels. In data center infrastructure—helping licensing may be restricted to a contrast, typical enterprise storage IT administrators make dynamic particular hardware platform. Such architectures pool only a subset of connections across storage, servers, limitations make it challenging to the storage resources by stretching a and networks. respond quickly and flexibly to volume, or logical unit (LUN), across changing business conditions. a predefined set of drives. PB 2011 Dell Compellent storage special edition | dell.com/compellent dell.com/compellent | 2011 Dell Compellent storage special edition 9 Dell Compellent storage Dell Compellent storage technology New write Tier 1 Snapshot is designed to deliver the right data to the right application at the right time through a dynamic, virtualized storage pool that is always available to servers. Administrators Virtual Tier 2 can create the entire array as a single pool pointer Read-only of high-performance storage or configure hours 24 particular subsets of the array as individual pools. Unlike typical enterprise storage systems, in which administrators must Tier 3 confine sub-LUN tiering to a distinct set of drives with predefined storage ratios for each tier, all Dell Compellent storage Figure 1. Data Progression software writes all data to tier 1, yet snapshots automatically move to a lower participates in the automated tiering. tier—freeing space on high-performance drives for mission-critical applications. Virtual pointers use block metadata to retain data continuity among associated blocks. Granularity and system intelligence facilitate precise data movement capacity). This block-level intelligence is migration cycle. Moreover, the migration The Dell Compellent array facilitates a designed for negligible system overhead process—which occurs automatically or highly granular approach that enables while helping to ensure that data always on demand—runs in the background while data movement with great precision and stays in tune with application needs. the system is online to avoid affecting data efficiency within the tiered environment. Typical enterprise storage architectures availability or application performance. Dell Compellent technology divides data limit which blocks can migrate because In storage approaches that do into pages—preformatted collections of they move data between tiers but do not not provide a comparable degree allocated and unallocated disk blocks. The offer more than one RAID level within each of flexibility, volumes are not easily pages are 2 MB by default (with 512 KB and tier. Moreover, they may require a server- expanded. As a result, administrators may 4 MB options). Details about each block are side agent to determine whether data need to compress data as volumes fill up captured in action at the 512-byte level, the should be moved. Because the agent runs and decompress if data becomes active smallest addressable data block. periodically or on demand, the information again, which may delay access to vital The Dell Compellent Storage Center it collects may be outdated by data enterprise information. SAN identifies blocks that are eligible for migration time. movement based on access frequency. Snapshot integration accelerates Then it moves only the pages that include Advanced automation streamlines write and read performance those blocks to the appropriate tier or RAID tiering administration Not only does Dell Compellent level. In contrast, typical enterprise storage Data Progression enables fully Data Instant Replay™ software enable architectures use blocks ranging from 16 automated, profile-based sub-LUN tiering. continuous data protection, it also helps MB to 1 GB in size. If only a small quantity of Administrators apply custom or predefined to optimize performance in an automated data in the block changes, the system must policy-based profiles to drive data tiered storage environment. Data Instant move the entire block regardless of size. placement and movement on each LUN Replay creates snapshots, or Replays, that Dell Compellent storage continuously or group of LUNs. Profiles specify not only use minimal storage space because they captures use characteristics about each the tiers but also the disk types, rotational capture only data written to the volume block, including creation time, location, speeds, and RAID levels within each tier. since the previous Replay. access frequency, and data type. This Administrators can change profile By default, Data Progression writes new in-flight metadata enables Data Progression settings, expand volumes on the fly, and data to tier 1, RAID 10 storage for optimal to determine what pages should be moved to add capacity without system disruption. write performance. Over time, it converts a different storage tier (freeing capacity in When drives are added to a tier, the infrequently accessed data blocks to read- the higher-performance tier) or a different Dell Compellent system is designed to only and moves them to a lower storage RAID level within an existing tier (sustaining automatically restripe all data across tier and RAID level, or to a different RAID read performance while reclaiming appropriate RAID levels during the next level within the same tier—freeing space 10 2011 Dell Compellent storage special edition | dell.com/compellent on the higher tier or RAID level. Migration within by providing a comprehensive view of the entire the same tier maintains read performance. To Dell Compellent storage environment, including further free tier 1 space, Replays automatically real-time tiering statistics. Following initial setup, move to a lower tier during the next migration tiering functionality is designed to be fully cycle. Because most enterprise data tends to be automated. However, at any time administrators inactive, organizations may reclaim significant may configure and control the tiered storage Fluid Data storage capacity from more expensive tier 1 storage without system disruption. makes sense for simply by migrating read-only data to a lower Because Data Progression is not tied to WhereToLive.com storage tier. any particular Dell Compellent storage system Ben Higginbotham, director of When new data needs to be written to model or platform—a common limitation with new technology, shares his passion a once-inactive block, Data Progression other approaches to sub-LUN tiering—it enables for what he calls “world-changing” automatically allocates a new writable block to organizations to scale up and out freely without Fluid Data technology. tier 1, RAID 10 storage, incurring no write penalty incurring downtime. Incorporating automated dell.to/inAxX5 for migrating data to lower tiers. Virtual pointers tiered storage into an existing Dell Compellent maintain continuity between associated blocks system does not require a costly, large-scale (see Figure 1). upgrade; it is as easy as activating that particular Unlike typical storage system architecture, built-in software module. Nor do