Data Migration: EMC, Compellent, 3PAR, FalconStor

A number of storage vendors implement storage tiering with automated data migration based upon user-defined policies. The following vendors implement migration in one way or another, and while they differ in subtle ways -- such as the granularity of data being migrated -- they implement the goal of migration with performance and cost in mind.

The following discussion is not intended to be a pro or con of any vendor, but instead offer a generalized comparison of each product’s interesting capabilities.

EMC FAST

EMC has received a considerable amount of attention since its introduction of FAST, or Fully Automated Storage Tiering. EMC’s target-based solution permits the transparent and policy-driven migration of storage objects between three tiers (representing flash, FC, and SATA).

The initial introduction of FAST provides LUN-level migration between tiers, but EMC’s upgraded FAST technology will very soon support sub-LUN level migration (1GB chunks of data). The upgraded FAST (due mid year 2010) also includes what’s called the “FAST Cache,” which introduces high-performance flash drives to reduce response times.

Compellent Data Progression

Compellent’s target-based solution for data migration in a tiered storage environment is called Data Progression. In addition to offering automated migration of data, Compellent supports up to 9 tiers based upon drive type (and rotational speed) and RAID level implemented in the tier. Compellent even implements what they call “Fast Track” for rotating media which places the most frequently accessed data within a tier to the faster tracks of each drive. This provides not only migration across tiers, but also optimizes within a tier to reduce seek times of the most active data.

The granularity of blocks that are migrated within Compellent’s architecture are 512KB, but can be tuned to up to 4MB depending upon the particular application.

3PAR Dynamic Optimization

3PAR implements target-based data migration using what they call Dynamic Optimization within their tiered storage architecture (called Autonomic Storage Tiering). 3PAR’s solution provides both LUN and sub-LUN migration of large blocks across tiers of SSDs, high-performance FC, and enterprise SATA drives.

This includes wide striping of data across SATA drives for the best performance in the capacity tier, and radial placement within the inner and outer tracks of rotating media for optimum performance. Within a tier, 3PAR permits the modification of RAID levels for a given volume for improved protection or performance.

FalconStor Data Migration

FalconStor provides a network-based solution for data migration within the Network Storage Server (NSS). NSS is a SAN-based virtualization platform that can be inserted into a SAN (FC and iSCSI). FalconStor implements LUN-based data migration (with synchronous block-level mirroring occurring underneath). LUNs continue to be available while the migration takes place (based upon administrator request), leading to no downtime of LUN availability. Further, this mirroring process can occur for legacy LUNs of arbitrary formats.

FalconStor’s NSS also works with their new HyperFS file system, which enables large capacity storage (up to 144PB) and access to billions of files.

Other Data Migration Solutions

While four vendors were discussed in this article, data migration is being implemented by a variety of vendors in their storage products. Other vendors include IBM, HP, Hitachi, Dot Hill, Pillar, Sun, Fujitsu, and others.

Data Migration Overview

The massive growth of archive data clearly identifies the need for storage tiering and the dynamic ability to migrate data between tiers for the best cost and performance benefit. From the vendor discussions, it’s easy to see that there’s a considerable amount of innovation occurring around data migration and other increasingly important storage services as it is, and will be a growing problem in the future.

While automated storage tiers and data migration are becoming checklist items for storage vendors, research continues to identify new optimizations and benefits while seamlessly integrating with other advanced features. You can read about some of this research in resources section at the end of this article.

Storage Tiers and Automated Data Migration

As is the case for most technology domains, change is the only constant. The storage ecosystem is a great example, where change is not only occurring, but at all levels -- from the individual storage devices to the baseline services and front-end protocols used to manipulate our growing masses of data.

In the following pages I'll explore some of those services and along the way touch on many of the related evolutions and revolutions that are happening today.

From a 30,000-foot view, automated data migration is about optimal placement of data. This optimization is a joining of the current characteristics of the data to the desired characteristics of the storage medium. For example, placing hot data on high-performing solid-state disks (SSDs) and cold data (or archive data) on cheaper storage such as SATA drives.

What makes this a challenge is that both elements have a tendency to change over time. New data tends to be used more often, but over time as it ages, it’s used less frequently. Further, storage mediums continue to evolve and diversify, creating new opportunities for storage tiers and matching data to storage characteristics.

Data migration is also useful in the context of advancing storage systems. Data migration provides the transparent ability to migrate data from an aging storage system to a new storage system, even online while users continue to make use of the storage in motion.

Let’s begin our discussion of storage tiering and data migration with an introduction to modern storage systems and their fundamental characteristics.

Storage Characteristics

Storage subsystems rely on a number of tricks to improve performance, typically based on caching and striping data, but ultimately their performance is a function of the storage medium. For this discussion, we’ll focus on a few drive examples that have different characteristics to later lead us into the purpose behind storage tiers.

Next Page: Storage drive comparison