Busting 6 Myths About Tiered Storage

The tiering of storage is a valuable tool for reducing costs and improving efficiencies in many ways. There are different levels of tiering, and the value that we derive from tiering can vary depending on the different types of tiering. There are also several myths about tiering of storage that need to be addressed.

Myth number 1: Tiered storage is information lifecycle management

Information lifecycle management (ILM) was marketing hype that was popular several years ago. The movement of data across tiers of storage is not ILM. The management of information must be done by an application or a records manager, not by storage infrastructure. Tiered storage may be a tool for information lifecycle management, but it does not make the decisions about information lifecycle management.

Myth number 2:  Tiering of storage is based on the value of the data

All data that we store is valuable, otherwise the data should be deleted and scrubbed from the storage. The notion that some data has less value and can be stored on cheaper, less reliable, storage is not acceptable. Storing data is useless if you cannot retrieve it. Data will have different response time and availability requirements during its life, and so we might need some data on Flash drives, and some could be stored on lower cost modular storage systems with 99.9% availability versus 99.999% availability, but all data must be stored on reliable storage systems that are protected.

Myth number 3: The most economical tiering is done within a storage frame

This is an argument that is made by vendors who do not have the ability to tier storage across multiple storage frames to optimize cost. This could be true if you do not have a need for tier 1 performance, availability, and scalability, and can fill all your requirements with a modular tier 2 storage frame with a mix of performance disks.

But if you need tier 1 storage, you will need a tier 1 storage frame with multiple processors that can access a global cache. A tier 1 storage frame could also contain a mix of different disk types. However, the frame costs for storing lower cost disks like SATA disk is higher than if you stored them in a lower cost modular frame.  It is true that the additional cost of another storage frame, even if it is a lower cost storage frame does add cost, but there is a cross over point where the addition of external storage for lower tiers of storage becomes more economical than adding disks to the tier 1 storage frame. Having the option of tiering across internal and external tiers of storage gives you the most flexibility to reduce costs.

Myth number 4: There is such a thing as Tier 1.5 storage

Tier 1.5 is a term that some analysts came up with to describe scale out storage. The reason for the 1.5 rating is to imply that this type of storage has tier 1 scalability, performance, and availability with the cost and ease of use of tier 2 storage. This type of storage consists of a loose coupling of two controller, tier 2 storage frames across an external switch using some protocol like Ethernet or Rapid I/O. The basic component here is a tier 2 storage system, and no matter how many other tier 2 storage systems are clustered together, it does not increase the scalability, performance, and availability of an application that is running on a particular storage frame. Applications can only access the storage resources, including tiers of storage, which are tightly coupled behind the cache that it is connected to. The loose coupling of storage frames makes it easier to sell more storage; it doesn’t help an application that needs more storage resources.

Myth number 5: There is such a thing as Tier 0

Since the introduction of Flash disks, many people refer to this type of media as tier 0 since it has higher performance that the highest performance spinning disk. In my view, tier 1 is the highest performing tier of media, whether it is a flash drive or a hard disk. Tier 0 means having no tier, nada, in the storage and should be reserved for performance tiers that do not reside in storage frames, such as flash cache products like Fusion I/O. While this is my perspective, I doubt if my opinion will change this myth.

Myth number 6: Hierarchical Storage Management is the same as storage tiering

See this post on HSM to see why they are different.

Do you agree? Disagree? Are there any other myths you can think of?

*Reproduced from the Hitachi Blog.