Solid State Drives Take Out the Garbage

“Flash’s Software Problems

“Handy said the erasure difficulty stems from the fact that all
of today’s software was written for HDDs, which don’t behave like
the flash in an SSD.

“”An HDD can overwrite existing data with new data,” said Handy.
“Since the software doesn’t accommodate flash’s
‘erase-before-write’ needs, the controller inside the SSD must take
care of this bit of housekeeping. Unused and unerased blocks are
moved out of the way and erased in the background.”

“The main advantage of background garbage collection is the gain
in write performance, said Geonyoung Hong, vice president of
Indilinx.

“”Background garbage collection will not degrade the performance
of an SSD if it does not stall ATA command processing from the
host,” said Hong. “The background garbage collection is
kick-started by a pre-set idle period and by calculating the cost
of garbage collection at that time.”

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