Tiered storage, or hierarchical storage management (HSM), is a data storage technique, which automatically moves different categories of data data between high-cost and low-cost storage media to reduce total storage cost. Typical technology and data varies by tier and categories of data. Categories may be determined by performance requirements, levels of protection needed, frequency of use, and other considerations.

Tier 0 – High Performance Storage

Highly valuable, mission critical data and “hot” transactional applications requiring extremely high performance stored on solid state drives. This data needs to be captured, analyzed and presented at the highest speeds.

Average Selling Price range: $50-100 per GB
Typical Technology Used:
• SSD – DRAM
• SSD – Flash memory
– offers the highest levels of I/O device performance
– most expensive tier on a $/GB basis
– most cost effective on a IOPs/$ basis

Tier 1 – Primary storage

Revenue generating and customer facing applications require high availability, high performance with near-zero downtime and fast Recovery Time Objectives (RTO).

Average Selling Price range: $7-20 per gigabyte
Typical Technology Used:
• Fibre Channel
• HDDs – provide lower cost per gigabyte than SSDs

Tier 2 – Secondary Storage

Tier 2 supports databases, file systems, backup, disaster recovery, email and other major business applications. The active business data on this tier doesn’t require sub-second response like Tier 1 or Tier 0, but reasonably fast response still is needed.

Average Selling Price range: $1-8 per gigabyte to $.20 to $2.00 per gigabyte
Typical Technology used: 
• Midrange disk arrays – SAS
• Midrange disk arrays – SATA
• LTO Tape

Tier 3 – Long Term Storage, Data Retention and Archive 

Content that is accessed infrequently such as archive data. Because of government and industry regulations, Tier 3 is the fastest growing segment of the storage industry at nearly 60% compounded annually. Tape offers WORM (Write-Once-Read-Many) capabilities and has led the way by implementing encryption for data at rest. This has enhanced its position as a storage medium for compliance, legal and any types of sensitive files.

Many major storage vendors offer a variety of tiered storage options but do not offer tape in Tier 3. In reality, their offering is a “disk only” solution. Using disk in Tier 3 is not cost effective because it forces archival, lower activity data to reside on spinning disks. Data that is inactive should not consume energy. 

Average Selling Price range: $.20 to $2.00 per gigabyte
Typical Technology used:
• Tape

For more information about Tiered Storage, download the Understanding Tiered Storage White Paper.

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