Greg explains this Hugepage Block Device driver, "The HPD driver implements a dynamically configurable RAM based block device which uses the kernel hugepage infrastructure and magazines to provide the memory based backing for the block devices. It borrows heritage from the existing brd ramdisk code with the primary differences being dynamic configurability and the backing methodology...the HPD driver may offer one of the most useful applications of this [Hugepage] infrastructure. There are obvious advantages in a ramdisk to handling the backing store in larger size units and NUMA support falls out naturally since the hugepage infrastructure is NUMA aware."
In terms of the relevance to the Linux storage industry with this HPD driver, "We have found the driver to be particularly useful in testing our SCST implementation, extensions and infrastructure. It is capable of sustaining line-rate 10+ GBPS throughput which allows target infrastructure to be tested and verified with FIO running in verify mode. The NULLIO target, while fast of course, does not allow verification of I/O since there is no persistent backing. Measured I/O latency on 4K block sizes is approximately five micro-seconds. Based on that Izzy thought we should get this released for our fellow brethren in the storage appliance industry. He suggests that pretty impressive appliance benchmark numbers can be obtained by using an HPD based cache device with bcache in writeback mode..... :-)"
More information on this just-announced block device driver can be found via the kernel mailing list.