Tiered storage: A look at internal and external tiered storage models

Tiered storage tools can help organizations meet information lifecycle management (ILM) goals. Learn about the internal and external tiered storage tools available from 3PAR, EMC, HDS and IBM.

What you'll learn: For organizations hoping to achieve information lifecycle management (ILM) goals, finding a solution that meets their specific policies, processes and practices can be difficult. Learn how tiered storage tools can help organizations meet these goals in a cost-effective and practical way.

By assigning different categories of data to different types of enterprise data storage media, tiered storage tools aim to reduce overall storage costs. While tiered storage is not a complete information lifecycle management solution, it does play an important role in a successful ILM hierarchy. As one vendor puts it, "ILM is all about having the right storage at the right time at the right cost."

For tiering data within a storage array, 3PAR Inc., EMC Corp. and Hitachi Data Systems (HDS) Corp. all offer a LUN virtualization component, which allows data stored on high-performance disk to be migrated online to lower-performance disks and vice versa based on pre-set policies and I/O patterns.

All three of these storage vendors support some sort of online LUN migration technique and all require a separate piece of hardware or a virtual machine (VM) that monitors the storage and initiates LUN migrations based on pre-set policies.

On the software solution side, 3PAR implements storage tiering through its Utility Data Lifecycle Management (DLM) product. Utility DLM uses templates, virtual copy and remote copy services to migrate data between tiers on the array both locally and remotely. The Utility DLM software can run on a Linux or Windows workstation, and all of the heavy lifting occurs on the array.

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For EMC's Virtual LUNs, data can be seamlessly migrated between RAID levels and disk types. The Virtual LUN technology can be managed by EMC's Symmetrix Control Center (SCC) if the customer is using a Symmetrix V-Max. EMC's Fully Automated Storage Tiering (FAST) or its Navisphere Management Suite (NMS) for the CLARiiON line can be used to manage the virtual LUN migration based on policies and data access patterns for the Clariion CX-4 line. Both SCC and NMS require Windows hosts.

Hitachi also has a software-based tiering solution simply called Tiered Storage Manager, which supports LUN migration between tiers in a virtualized storage pool. The pool can include other vendors' arrays attached to the Hitachi USP storage array platform.

External tiered storage tools include IBM's SAN Volume Controller (SVC), EMC's Invista and Hitachi's USP-V.

SVC is an xSeries based "I/O engine" architecture that acts as a front end to all SAN storage. The SVC can front-end any Fibre Channel-attached storage array regardless of vendor and can provide iSCSI connectivity on the front end as well as Fibre Channel (FC). LUNs can be seamlessly migrated within and across back-end arrays, allowing customers to provide one vendor for Tier 1, another for Tier 2 and so on if their environment dictates heterogeneous storage.

EMC's Invista also utilizes external nodes, but the twist is that it also uses an intelligent SAN switch (or linecard), and each LUN on the back-end array has a virtual address that is presented to the host. EMC considers this solution to be operating at Layer 2 in the Open Shortest Path First (OSPF) model and is touted as "network-based volume management."

Hitachi's USP-Vis the company's high-end line of storage arrays; the LUN virtualization occurs within the storage controllers and does not require any external components. Typically, customers include the Hitachi Hi-Command server, which is comparable to EMC's NMS or SCC. Hi-Command and the Tiered Storage Manager software are required for LUN migrations, and these migrations can be performed between arrays online with no disruption to hosts.

All of the tools discussed have been SAN infrastructure-level components and can certainly be considered ILM. All of the tools are policy-based, either by application requirements, age requirements or cost requirements; all are storage-centric; and all support live data migration in a transparent way. To be successful, storage tiering tools should have as little impact as possible on the user's experience, and the storage vendors are clearly showing that they can provide this service to aid IT in its pursuit of ILM.
 

This was first published in February 2010

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