Log-structured Caching for Linux
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dm-writeboost Gitter

Log-structured Caching for Linux


dm-writeboost is originated from Disk Caching Disk (DCD). DCD, implemented in Solaris, is an OS-level IO controller that builds logs from in-coming writes (data and metadata) and then writes the logs sequentially similar to log-structured filesystem. dm-writeboost implements the concept on Linux's device-mapper in more sophisticated way. As a further extension, dm-writeboost supports read-caching which also writes data sequentially.



  • Durable: Any power failure can't break consistency because each log consists of data, metadata and the checksum of the log itself.
  • Lifetime: Other caching software (e.g. dm-cache) separates data and metadata and therefore submits writes to SSD too frequently. dm-writeboost, on the other hand, submits only one writes for hundreds of data and metadata updates so the SSD lives longer since SSD's lifetime depends on how many writes are submitted.
  • Fast: Since the sequential write is the best I/O pattern for every SSD and the code base is optimized for in-coming random writes, the write performance is the best among all caching drivers including dm-cache and bcache.
  • Portable: All kernel version 3.10 or later is supported with minimum compile-time macros.


  • Install: sudo make install to install and sudo make uninstall to uninstall. sudo make uninstall MODULE_VERSION=xxx can uninstall specific version that's installed. DKMS is required so please install it beforehand. (usually available in package system)
  • Make a device: Make a script to build a caching device. Please read doc/dm-writeboost-readme.txt for the dmsetup command detail. After reboot, you need to rebuild the caching device rather than reformatting as in the initial setup.

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Awarded by Japanese OSS Encouragement Award. Thanks!


Copyright (C) 2012-2018 Akira Hayakawa <ruby.wktk@gmail.com>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.

You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

Developer Info

Akira Hayakawa (@akiradeveloper)
e-mail: ruby.wktk@gmail.com