ORIGINALLY POSTED 16th September 2013
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Recently we published an IBM Redbooks Solution Guide on Implementing IBM Easy Tier with IBM Real-time Compression.
IBM® Easy Tier® is a performance function that automatically and non-disruptively migrates frequently accessed data from magnetic media to solid-state drives (SSDs). In that way, the most frequently accessed data is stored on the fastest storage tier, and the overall performance is improved.
How does it work
Every volume is split into logical units called extents. Easy Tier is based on algorithms that are developed by IBM Research, which evaluates the access frequency of each extent. Each extent is rated according to the number of I/Os going to that extent. Extents with a high rating, receiving the most I/Os, are marked as “hot” extents and become candidates for migration to SSDs in the same storage pool. Periodically, but no greater than 24 hours, a migration plan is created according to the “heat” of the extents and the data is migrated to the SSD MDisk. When the SSD becomes full, and there is a hotter extent to move onto the SSD, the “cooled” extents are migrated back to the lower-tiered MDisk.
Migrations are typically minimal, and add up to a maximum of two terabytes of data per day. The number of host read and write operations to a specific extent determines the rating of the extents. Only I/Os smaller than 64 KB are considered when determining ‘heat’ to prevent sequential I/O patterns from filling up the SSDs with data that is not likely to be accessed again frequently.
Read more here.