Tiered, Schmeared, Weird: Enterprise Storage Management Issues and Technologies

We've been doing research in the areas of enterprise storage management with a focus on what is now called Tiered Storage and EMC calls Information Lifecycle Management (ILM). The technology was also called, back in the day, Hierarchical Storage Management (HSM).

The basic idea is pretty obvious. Store the most critical, performance sensitive data on devices that are the most reliable and highest performing (and most expensive). Store less critical data on less expensive devices and the least critical data on the least expensive and possible off line devices.

I'll probably address several of the aspects of these technologies in multiple postings over the next several weeks. For now, I'll just define some terms and establish a baseline context for the future. For these discussions most of the storage solutions mentioned will be shared. Sharing may be on a SAN, NAS or iSCSI protocol, but the devices themselves are shared.

First of all, lets describe the nature of the hardware typical to the different storage tiers. As mentioned previously, the logic behind tiered storage is that the most performance sensitive, mission critical data should be stored on devices that offer the greatest reliability and performance. This generally means Fibre Channel Storage Area Networks with the largest arrays, fasted backplanes and connections. Vendors for these systems include IBM DS6000 and DS 8000, HP XP series, SUN StorageTek 9900 series, EMC Symmetrix, Hitachi Universal Storage Platform, Pillar Axiom, and a few others.

The second storage tier, at least for purposes of this discussion, consists of systems that are not as powerful as the top of the line products. They are intended for servers and applications where maximum performance is not the key driver. The hardware can be the same as previously, listed, perhaps with lesser components, or be older models. Depending on the scale of the organization, these devices could also be the same vendor's mid-range systems. For example, HP EVA or EMC CLARiiON. This tier also opens the door for additional vendors and connection protocols. For example, NetApp filers. (I know that NetApp makes high end devices and could be included in the previous list, but this discussion is already very complicated.)

The next tiers bring us to another aspect of the story: online, near-line and offline storage. Quickly, online storage is that which is connected to and immediately available to the devices needing the data. Near-line is storage that's connected, but which may not be immediately available for use, such as a Magstar tape used in legacy mainframe systems. Offline storage is data that needs to be brought online before it can be accessed. This can be as sophisticated as a DVD stored in an automated library or as simple as a tape stored in a vault. The tiers being discussed now can consist of any combination of devices that fit into these three states depending upon need and design.

My next post will discuss some of the ways vendors are attempting to both provide tiered storage solutions. In the future, I'll be looking at solutions from vendors who purport to provide alternatives that greatly simplify this architecture such as XIV Nextra, and perhaps drill down into some of the technical details. I'll also be discussing how the various vendors go to market with their interpretations of these themes. Not to belabor the obvious, but each vendors strategy exploits their history, market and product strengths.