I’m going to assume you already have a file system and you just want to add caching. Instead dm-cache sits on top of your existing file system or you create a new file system. One of the nice things about dm-cache is that it doesn’t require you to create a new block device to store your file system on. It easily translates to other distributions, but users will need to find a sufficient kernel and modify the init scripts to fit their init system. This tutorial is going to cover the basic steps to setup dm-cache on a Ubuntu 13.04 machine. The goal is to significantly speed up throughput and latency to frequently accessed files. A good compromise.ĭm-cache is a device-mapper level solution for caching blocks of data from mechanical hard drives to solid state SSDs. For reference, running git grep blah on a recent kernel tree takes 25-30 seconds on traditional HDD, 2 seconds on a SSD and 4 seconds on the same HDD + SSD + dm-cache with a warm cache.

I’ve played with lvmcache and like it, if I have time I’ll write-up a blog post regarding performance.

Also consider Richard Jones’ LVM Cache blog post for a guide that approximates the man page.

For more documentation on lvmcache consider man lvmcache if your lvm2 package is up to date and has cache support.

Arch Linux bug 40754 and the 41291 dupe I reported will track the currently missing feature in Arch Linux.

At the time of this update, it appears that only Fedora (and derivatives) have support.

The latest lvm2 tools have support for lvmcache which is a front-end to dm-cache and is much easier to use.

Modern distros have kernel support for dm-cache out of the box, so don’t worry about updating the kernel.

Consider it more of a behind the scenes guide for dm-cache from the early days. Many of the following steps in this post are no longer required or recommended.

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