Making a SSD working as a Cache for a HDD with bcache.

Bcache Tutorial

There are 3 Methods for using a SSD as cache.
dm-cache, bcache,enhance-io all three should be avaliable in Kernel Version 3.10.
Performance differenceses are discussed here => http://lkml.indiana.edu/hypermail/linux/kernel/1306.1/01246.html
In this tutorial I will use bcache since dm-cache didn't worked for me.
At the moment there is only an rc5 candidate for kernel 3.10.0
How to compile it is explained below. If you have a newer kernel than 3.10 and it is bcache enabled you dont need to compile it by yourself. In this case just jump over the kernel-compile-exlanation. If your kernel is compiled with bcache support you can test with "modprobe bcache". If that doesnt throw an error it should work :)
I will link to the tutorials I used. If you found better ones please paste a link in the comments

How to compile a kernel by yourself is explained at:
=> http://bodhizazen.net/Tutorials/kernel

I used Fedora 18. If you got it done in another distribution you may want to do a fork of this tutorial and change the stepps which differs.
In short the steps are:
sudo yum-builddep kernel
sudo yum install xz tar ncurse
wget https://www.kernel.org/pub/linux/kernel/v3.x/testing/linux-3.10-rc5.tar.xz
tar xvf linux-3.10-rc5.tar.xz
cd linux-3.10-rc5
make oldconfig

hold enter until everything is choosen

make menuconfig

go to "device drivers" -> "Multiple devices driver support (RAID and LVM)" -> "Block device as cache" enable it!
save and exit

make -j20
make -j20 modules
sudo make modules_install
sudo cp arch/x86/boot/bzImage /boot/vmlinuz-3.10.0-rc5
sudo cp System.map /boot/System.map-3.10.0-rc5
sudo cp .config /boot/config-3.10.0-rc5
sudo dracut /boot/initramfs-3.10.0-rc5.img 3.10.0-rc5
sudo grub2-mkconfig -o /boot/grub2/grub.cfg #this path can be other just search for grub.cfg in /boot " find /boot -iname grub.cfg" #this differs from the tutorial because the tutorial is for an old Fedora Version

Now try to reboot and test if the new kernel boots
when this works you are done half of the way
You now need a clear SSD and a clear partition on the HDD you want to cache.
But first things first.

sudo yum install git libuuid libuuid-devel
git clone http://evilpiepirate.org/git/bcache-tools.git
cd bcache-tools
make
sudo make install

this should it be.
Now you can follow http://atlas.evilpiepirate.org/git/linux-bcache.git/tree/Documentation/bcache.txt?h=bcache-dev

In short: #Please of course use the devicenames of your own devices!
modprobe bcache
make-bcache -B /dev/mapper/fedora_virthost-home 
make-bcache -C /dev/sda1
modprobe bcache
echo /dev/mapper/fedora_virthost-home > /sys/fs/bcache/register
echo /dev/sda1 > /sys/fs/bcache/register
mkfs.ext4 /dev/bcache0
mount /dev/bcache0 /home   #you can mount it whereever you want it!
ls /sys/fs/bcache/  #get uuid
echo 766e3ca5-f2db-44c9-97cc-13a97b32d348 > /sys/block/bcache0/bcache/attach #The number is the uuid from previous step

Now you should have a working partition in /home (or whereever you mounted it)
But this is just till the next reboot
so lets make it peresistent
place the following script in /etc/init.d/bcache

cd /etc/init.d/
sudo yum install nano
nano bcache

and copy everything between the lines in the file...
customise the marked lines
------------------
#!/bin/bash
# chkconfig: 2345 20 80
# description: Mounting bcache on /home

# Source function library.
. /etc/init.d/functions

start() {
	modprobe bcache
	echo  /dev/mapper/fedora_virthost-cache  >  /sys/fs/bcache/register #please customise!!!!
	echo /dev/sda1 >  /sys/fs/bcache/register #please customise!!!!
	mount /dev/bcache0 /home    #please customise!!!!
}

stop() {
	umount /dev/bcache0 /home #please customise!!!!
}

   case "$1" in 
    start)
        start
        ;;
    stop)
        stop
        ;;
    restart)
        stop
        start
        ;;
    *)
         echo "Usage: $0 {start|stop|restart}"
   esac

   exit 0
------------------

close and save (Strg + x and enter)

chmod +x bcache
systemctl enable bcache.service

reboot

now we test if it is there again with

df -h|grep bcache

there should be something like this
/dev/bcache0                      852G    255G  554G   32% /home
Thats it have fun.

Thanks for all the tutorials/websites i used below.
https://wiki.archlinux.org/index.php/Bcache
http://unix.stackexchange.com/questions/62501/where-can-i-find-a-good-tutorial-for-installing-bcache
http://atlas.evilpiepirate.org/git/linux-bcache.git/tree/Documentation/bcache.txt?h=bcache-dev
http://bcache.evilpiepirate.org/#index2h3
http://evilpiepirate.org/git/bcache-tools.git
http://evilpiepirate.org/git/linux-bcache.git
http://lkml.indiana.edu/hypermail/linux/kernel/1306.1/01246.html
http://bodhizazen.net/Tutorials/kernel
https://www.kernel.org/

I not tested the tutorial so I may forgot a step. If that happend or you find a bug please let me know in the comments!
I will correct it.
I just didn't found a straight forward tutorial so I made one after I got it done.
So all these steps are reproduced and NOT tested!

Have fun Jakob Oesterling