This is the successor to memDiskTransfers, reporting memory-to-disk paging transfers per second, per 'Memory to Disk transfers/sec,' also typed as INTEGER rather than DisplayString for the same reason as memSwapsSec64. It tracks the disk-I/O consequence of the same memory shortage flagged by memSwapsSec64, so the two should rise and fall together; if they diverge, that's worth investigating as a possible disk subsystem issue independent of memory pressure. Elevated values here without a corresponding rise in memSwapsSec64 would point to non-swap disk activity (like heavy logging) rather than memory exhaustion.