bcache was rolled into the 3.10 mainline kernel. I’ve just installed CentOS 7 with
3.10.0-123.4.4.el7.x86_64. However, after creating the cache devices I realised they were’t attached. Turns out
/sys/fs/bcache doesn’t exist – ie it’s not enabled in the kernel, but why? I believe it’s enabled by default in Ubuntu/etc…
Red Hat Enterprise Linux 7 was forked from Fedora 19, and in that release bcache support was minimal, experimental and buggy. It currently isn’t planned to be complete until Fedora 22. As a general rule, Red Hat does not ship features in RHEL which aren’t production-ready, even as a technology preview.
If I were to guess, I would expect to see this appear in RHEL as a technology preview sometime around 7.2, or 7.3, or perhaps even 7.4, depending on how development progresses — and importantly, depending on whether Red Hat customers ask for it… or more likely I’m totally wrong.
bcache is another option available in the Fedora 22 Linux distribution and merged into the upstream Linux kernel. It is not currently viewed by Red Hat as Enterprise ready as a supported technology.
Red Hat instead supports dm-cache and lvmcache as of RHEL 6.7 and 7.1.
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