Testing The BCache SSD Cache For HDDs On Linux 4.8

It has been over one year since last testing the mainline Linux kernel's BCache support for this block cache that allows solid-state drives to act as a cache for slower hard disk drives. Here are some fresh benchmarks of a SATA 3.0 SSD+HDD with BCache from the Linux 4.8 Git kernel.

While we've written about BCache dozens of times on Phoronix, if you are unfamiliar with this Linux block cache see the project site, Wikipedia, or the always-thorough Arch Linux BCache guide.

For this Linux 4.8 kernel based testing the Hitachi HUA72302 HDD was acting as the main storage device while the Samsung 850 EVO 120GB SATA 3.0 SSD was acting as the cache. The Hitachi UltraStar drive has 2TB of storage, 7200RPM, 64MB cache, and SATA 3.0. With this BCache testing I tested it with its writethrough, writeback, and writearound modes while also testing with/without the SSD discard option.

Compared to this Samsung SSD + Hitachi HDD BCache setup with the different options was a Samsung 950 PRO NVMe SSD, Intel 600P 256GB NVMe SSD, the Samsung and Hitachi drives alone, a PNY CS1211 120GB SATA 3.09 SSD, OCZ Trion TR150 120GB SATA 3.0 SSD, and an Intel SSDSC2BW12 120GB SATA 3.0 SSD. The assortment of standalone drives provide better perspective for the overall Linux disk performance as opposed to just featuring standalone the HDD and SSD used with this BCache setup.

All of the benchmarks for this article were carried out in a fully-automated and reproducible manner using the open-source Phoronix Test Suite benchmarking software.