QuickStart Recipe for Ubuntu 11.10

This page describes setting up and removing Flashcache on Ubuntu 11.10 using an existing root partition. It looks like there is a bug in the github wiki parser that combines all the lines. Until they fix it, just view the source to use this document.

Table of Contents Resources Instructions Setting up flashcache on a md device Removing Flashcache from a Boot Volume

Resources

• https://github.com/facebook/flashcache/blob/master/README-DKMS
• https://wiki.archlinux.org/index.php/Flashcache

Instructions

# Install pre-reqs
apt-get install git build-essential dkms linux-headers-`uname -r`

# Get flashcache source
git clone https://github.com/facebook/flashcache.git

# Add the "lazy" create option here:
wget https://github.com/guppy/flashcache/commit/1ea19b6fbf453e1e2955aef5488c708f5191ca68.patch
patch -p1 <1ea19b6fbf453e1e2955aef5488c708f5191ca68.patch

# Build and install the source (as root)
make -f Makefile.dkms

Setting up flashcache on a md device

# Install boot support
make -f Makefile.dkms boot_conf

# Find the UUID of the volume you want to cache:
ls -la /dev/disk/by-uuid/

# Create the flashcache device
# Assuming /dev/sdb is your flashcache SSD, replace with your actual device
flashcache_create -v -l -p back -b 4k fc-md /dev/sdb /dev/disk/by-uuid/(UUID_FOUND_ABOVE)

vi /etc/fstab
# Comment out the line with the device you want to cache
# Add a new line for the flashcache similar this:
/dev/mapper/fc-md / ext4 relatime,nobarrier 0 1

# Update the initial RAM disk to add the FC modules and helper apps
update-initramfs -k ALL -u

# Set some optional options
vi /etc/sysctl.conf

#####################
# flashcache settings
#####################

# disable writing dirty cache data at shutdown (do this only if you really trust FC)
dev.flashcache.fast_remove = 1

# change the reclaim policy to LRU from FIFO 
dev.flashcache.reclaim_policy = 1

# do not write "stale" data to disk until evicted due to lack of space
dev.flashcache.fallow_delay = 0

# reboot and enjoy the speed

# Test with 
ls -la /dev/mapper/
# To see which device is fc-md
# Then
iostat 
# To see that the fc-md device is seeing the same i/o as the underlying block device

Removing Flashcache from a Boot Volume

# First, ensure that dev.flashcache.fast_remove = 0 and reboot to minimize potential lost data
# Edit fstab
vi /etc/fstab
# Comment out the flashcache line and un-comment the original device line

# Reboot to recovery mode (hold left shift during boot)
# Mount / using the non-flashcache drive
mount -o relatime /dev/md0 /

# Remove the FC device mapper device
dmsetup remove fc-md

# Remove FC special SSD signature (change /dev/sdb with whatever your FC device is)
flashcache_destroy /dev/sdb

# Done, continue booting normally
exit