It follows that various embodiments described herein may preferably be implemented in combination with a NAND based memory controller which is capable of tracking the heat of data. For example, NAND based memory controllers described herein may be able to track the heat of logical and/or physical pages, memory blocks, etc. However, it should again be noted that various embodiments herein may be implemented with a wide range of memory mediums, e.g., NVRAM based SSD controllers, and the explicit description of NAND controllers is in no way intended to limit the invention.

Write Allocation

Write allocation includes placing data of write operations into free locations of open block-stripes. As soon as all pages in a block-stripe have been written, the block-stripe is closed and placed in a pool holding occupied block-stripes. Typically, block-stripes in the occupied pool become eligible for garbage collection. The number of open block-stripes is normally limited and any block-stripe being closed may be replaced, either immediately or after some delay, with a fresh block-stripe that is being opened.

During performance, garbage collection may take place concurrently with user write operations. For example, as a user (e.g., a host) writes data to a device, the device controller may continuously perform garbage collection on block-stripes with invalid data to make space for the new incoming data pages. As mentioned above, the block-stripes having the garbage collection being performed thereon will often have some pages that are still valid at the time of the garbage collection operation; thus, these pages are preferably relocated (e.g., written) to a new block-stripe.