---
name: "flashcache"
section: "7"
platform: "linux"
package: "flashcache-utils"
version: "3.1.3+git20150701-5"
release: "Debian 9 (Stretch)"
platforms: ["linux"]
url: "https://new.carta.tech/flashcache"
---

# flashcache(7)

overview of operation

## NAME

flashcache - overview of operation

## SYNOPSIS

modprobe flashcache

Flashcache consists of a kernel module and userspace utilities. The module is named "flashcache". The kernel module can be controlled with [*flashcache\_create*(8)](/flashcache_create/8.md), [*flashcache\_load*(8)](/flashcache_load/8.md) and [*flashcache\_destroy*(8)](/flashcache_destroy/8.md) utilities.

## DESCRIPTION

Flashcache is a block cache for Linux, built as a kernel module, using the device mapper. Flashcache supports **writeback**, **writethrough** and **writearound** caching modes. See [*flashcache\_create*(8)](/flashcache_create/8.md) for a description of caching modes.

Flascache allows one to use a fast block device such as Solid State Drives (SSD) as cache to accelerate a slower drive used as backstore.

Originally, Flashcache was built as a block device cache for I/O intensive database applications, for example to run an accelerated InnoDB store for [*mysqld*(8)](/mysqld/8.md), but it can be used as general purpose backend for filesystems as well.

## USAGE

Before using Flashcache, it might be a good idea to check if device mapper works properly. Assuming the partition /dev/md0p1 shall be used as flash cache, one may try to create a linear device with following command:

**echo 0 1024 linear /dev/md0p1 0 \| dmsetup create tmpdisk**

It this works, *flashcache\_create* should be able to create its device.

Remove tmpdisk with command:

**dmsetup remove tmpdisk**

Before creating a flashcache device using the *flashcache\_create* command, the deivce must not be mounted.

## SEE ALSO

[`flashcache_create`(8)](/flashcache_create/8.md), [`flashcache_load`(8)](/flashcache_load/8.md), [`flashcache_destroy`(8)](/flashcache_destroy/8.md)

*README* and other documents in **/usr/share/doc/flashcache-utils**. In particular, see **flashcache-sa-guide.txt** for configuring the flashcache kernel module through its */proc* interface.

The flashcache source code and all documentation may be downloaded from \<https://github.com/facebook/flashcache/\>.

## AUTHORS

Flashcache is developed by Mohan Srinivasan \<mohan@fb.com\>

This man page was written by Dmitry Smirnov \<onlyjob@member.fsf.org\> for Debian GNU/Linux (but may be used by others).