=============================== Device mapper cache utilities =============================== License: GPLv2+, see COPYING for details This project provides few simple scripts to simplify the usage of dmcache devices. These scripts are based on the work of Darrick J. Wong [1]. They have been rewritten and simplified to better fit our needs. I was also scared of getting my BIOS reflashed with rude poetry [2]. [1]: http://djwong.org/docs/dmcache-tools.tar.gz [2]: http://www.redhat.com/archives/dm-devel/2013-March/msg00057.html Commands ======== dmc-load -------- Load and activate dmcache devices defined in /etc/dmctab. Quite naturally, this command must be executed before mounting cached partitions. Hence, it's a good practice to set udev run it. See 86-dmc.rules. Usage: dmc-load [NAME] NAME - a name of the device mapper cache device defined in /etc/dmctab. If not given, load all dmctab entries. dmc-unload ---------- Deactivate and unload dmcache devices defined in /etc/dmctab. This is a logical counterpart of dmc-load and does reverse operations in reverse order. Usage: dmc-unload [NAME] NAME - a name of the device mapper cache device defined in /etc/dmctab. If not given, unload all dmctab entries. dmc-mklvm --------- Format a disk with LVM partitions suitable for dmcache devices. Usage: dmc-mklvm [-b CACHE_BLOCK_SIZE=512] VG PV CACHE_BLOCK_SIZE - the size of cache blocks. This is used to calculate the optimal size for the metadata device. Default is 512 sectors. VG - name for the volume group PV - physical volume for the volume group, e.g. a disk, a disk partition, etc. Setup example ============= Assumptions: - the cache disk (SSD-disk) is /dev/sda - the cached partition is /dev/mapper/main-home - 'cache-home' is the desired name for the cache volume group Run:: dmc-mklvm cache-home /dev/sda Add the following entry to /etc/dmctab:: cache-home /dev/cache-home/metadata /dev/cache-home/data /dev/mapper/main-home 512 0 default 0 Edit /etc/fstab to mount /home from the cache device by adding the following entry:: /dev/mapper/cache-home /home ext4 defaults 0 2 Remember also to comment or remove the previous /home mount entry:: #/dev/mapper/main-home /home ext4 defaults 0 2 Copy 86-dmc.rules to /lib/udev/rules.d if its not already there.