  For modern flash-based SSDs, the performance overhead of internal data
migrations is dominated by the data transfer time, not by the flash program
time as in old SSDs. In order to mitigate the performance impact of data
migrations, we propose rCopyback, a restricted version of copyback. Rcopyback
works like the original copyback except that only n consecutive copybacks are
allowed. By limiting the number of successive copybacks, it guarantees that no
data reliability problem occurs when data is internally migrated using
rCopyback. In order to take a full advantage of rCopyback, we developed a
rCopyback-aware FTL, rcFTL, which intelligently decides whether rCopyback
should be used or not by exploiting varying host workloads. Our evaluation
results show that rcFTL can improve the overall I/O throughput by 54% on
average over an existing FTL which does not use copybacks.
