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...
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1Because: Redhat. Sometimes they strip mainline kernel feature out of the distribution. – ewwhite Jul 28 '14 at 22:43
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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.
Red Hat's current stance on bcache is:
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.
Michael Hampton
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By default, centos 7 doesn't compile with bcache. You should compile and insert the bcache module manually. Then /sys/fs/bcache will show up. See http://10sa.com/sql_stories/?p=1052
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