Log-structured file systems: There's one in every SSD
Posted Sep 21, 2009 16:35 UTC (Mon) by farnz
In reply to: Log-structured file systems: There's one in every SSD
Parent article: Log-structured file systems: There's one in every SSD
It takes a little intelligence on the part of the SSD designer. Reads from a logical block not currently mapped to any physical flash must be defined as returning all zeros; once you've done that, you can treat writing a logical block with all zeros as a "free" operation, not a write. The "free" operation just marks that logical block as not mapped to any physical flash.
You then know you don't need to hang onto the data that used to be important to that logical block; initially, it's still there, but when you garbage collect the physical block that used to contain the bytes from that logical block, you don't bother copying the data.
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