$6\mathrm{.}17$ One trend in high$-$end servers is toward the inclusion of nonvolatile flash memory in the memory hierarchy, either through solid$-$state disks $($SSDs$)$ or PCI Express$-$attached cards. Typical SSDs have a bandwidth of $250$ MB$/$s and latency of $75\backslash$mu s$,$ whereas PCIe cards have a bandwidth of $600$ MB$/$s and latency of $35\backslash$mu s$.$