Dave Graham's Blog

In Part One of this Cloud Optimized Storage Solutions (COSS) series, we took a look at the content being stored on COSS and in Part Two at how it is stored.

Storage within the cloud is meaningless without a measurable level of performance that it can be compared against. Since there are no established benchmarks that determine performance of storage within a cloud infrastructure, it is reasonable to apply tiering metrics to storage based on content valuation and service level agreements (SLAs) and utilize this as an overarching methodology to judge COSS storage capabilities based on application set.

Within the concept of Information Lifecycle Management (ILM), there exists the idea that storage can be “tiered” based on criticality of need, application storage performance, or other derived metrics that couple relative responsiveness and bandwidth to serviceability. Layered over the top of this metric is the concept of aggrandized Service Level Agreements that cover compliance, data protection, and data access (to name a few). To bring things into more direct focus, there are 4 direct “Tiers” that are recognized (or promoted) within the storage community: Tier 0, Tier 1, Tier 2, Tier 3. While it is worthwhile to note that these Tiers are arbitrary in nature, they do provide a baseline framework upon which to build a more robust data service model.

The Data Tier Models

Tier 0 & 1: Performance & Availability Guaranteed Storage

Tier 0 is a relatively recent addition to the ILM tiering schema and is based solely on the emergence of Solid State Devices (Fusion I/O, EMC/STEC EFDs, et al.). These storage devices feature sub-millisecond access times coupled with extremely high bandwidth to the storage subsystems, thus driving a higher level of storage access and bandwidth metrics for applications such as Online Transaction Processing (OLTP) and Data Warehousing. The criticality of response to these applications is of a higher priority than Tier 1.

Tier 1 was originally established to service high availability, high bandwidth, low response time application and storage needs that tied directly to OLTP/OLAP, DSS, Data warehousing, etc. type workloads. Typically applications in this Tier have a sub-20ms response time requirement (or best practice) and are more sensitive to latency issues than, perhaps, Tier 2 workloads.

Tier 2: Availability Guaranteed Storage

Tier 2 is commonly referred to a transitional data tier, namely due to the nature of data that lives within it. Common data placement within Tier 2 centers on file systems or data that has a change rate that is based on occasional access within a fixed window of time (e.g. 30-60-90 days). It has a decided focus and tuning towards making sure that data is “online” and accessible without stringent latency or performance criteria.

Tier 3: Accessibility Guaranteed Storage

The last noted Tiering level for data is Tier 3. Tier 3 can best be described as an archive level for stagnant or “stale” data that has infrequent access. Historically, Tier 3 has been policy driven, that is, the recipient for some sort of data migration movements versus being a primary storage Tier for end-user access. Within the COSS environment, however, Tier 3 becomes as crucial of a storage target as Tier 1 or 2 simply due to the large preponderance of unstructured data within the cloud space.

Expectations of Data Tiering

The somewhat open-ended definitions to these data tiering levels are purposeful. In defining the principles of a COSS, there is an inherent need to keep them somewhat fluid especially as content continues to change and develop more complexity. Additionally, while the cloud currently has a majority stakeholder in unstructured data, there is no reason why structured data (and associated programmatic hooks and layers) cannot regain ground. As stated previously, these data tiers, while arbitrary, still provide an essential top-down view of how data can be categorized when planning for a COSS implementation. As an extension of data tiering, it’s also important to understand how global and particular Service Level Agreements (SLAs) can and will affect the data stored on COSS.

Author's Notes:

• ILM, to the best of my knowledge, is not an EMC-designed concept. Whether or not storage tiers existed before EMC popularized the term is indisputable and inherently inconsequential to this discussion.
• Disclaimer - The opinions expressed here are my personal opinions. Content published here is not read or approved in advance by EMC and does not necessarily reflect the views and opinions of EM

• An Introduction to Cloud Optimized Storage Solutions
• Cloud Optimized Storage Solutions (COSS) Explored
• EMC Creates New Cloud Category
• Virtualization Conference Europe 2009: 18-19 May 2009 in Prague
• Cloud Computing Expo: Cloud Optimized Storage Solutions