The phrase “Tier 1 data storage” sometimes causes confusion, because increasingly, the top layer in the tiered storage hierarchy is being referred to as Tier 0, thanks to the rise of technologies such as storage class memory and flash. However, for the purposes of this article, Tier 1 storage will refer to the storage tier with the highest performance.
Tier 1 data storage is designed for data which is highly time-sensitive, volatile, and must be accessed quickly—in as close to real time as possible. For example, in a stock trading environment, where huge amounts of money can be lost in an instant, only the fastest Tier 1 storage will work. Therefore, regardless of overall storage efficiency, at the Tier 1 level the storage media is typically very fast, solid state storage configured for the best possible performance, without regard to cost.
Tier 2 data storage. Tier 2 is typically used to store transactional support data for customer-facing systems such as retail applications, and other high-performance applications where only extremely short delays will work. A step down from Tier 1, a Tier 2 storage solution will usually utilize a more cost efficient storage system.
Tier 3 data storage. Tier 3 is used for hot data such as ERP and CRM data which users must access often without too much delay. Compared to Tier 1 and Tier 2, this usually means medium to high performance, high capacity hard drives at a low cost per Gigabyte stored and substantially more data.
Tier 4 data storage is where warm data from older emails and recently completed transactions goes—anything that needs to be accessed less often, but still regularly and without too much delay. Typical Tier 4 storage requirements include very large capacity and affordability, so high capacity, relatively low performance hard disk drive storage, such as SATA drives rather than high performance RAID arrays or SAS disks, are a more common solution.
Tier 5 data storage is for archiving cold data for the future. Since there is time to retrieve this kind of data and cost is the overriding factor here, cloud storage tiers, optical media, or disk and tape storage systems are great choices.