The MySQL backups using LVM Snapshots post is now by far the most popular post.
Here is shell script which helps get the Logical Volumes (LV) setup in the first place.
### START OF SCRIPT ###
#!/bin/sh
# Name: make_mnt_LV.sh
# Script to make EC2 /mnt into a LVM volume
modprobe dm-snapshot
umount /mnt
pvcreate /dev/sda2
vgcreate vg /dev/sda2
lvcreate -L30720M -n myvmdisk1 vg
mkfs -t ext3 /dev/vg/myvmdisk1
mkdir -p /data1/mysql/data
mount /dev/vg/myvmdisk1 /data1/mysql
lvcreate -L30720M -n myvmdisk2 vg
mkfs -t ext3 /dev/vg/myvmdisk2
mkdir -p /data2/mysql/data
mount /dev/vg/myvmdisk2 /data2/mysql
lvcreate -L30720M -n myvmdisk3 vg
mkfs -t ext3 /dev/vg/myvmdisk3
mkdir -p /backup/mysql/data
mount /dev/vg/myvmdisk3 /backup/mysql
lvdisplay
mkdir -p /data1/mysql/data
mkdir -p /data2/mysql/data
chown -R mysql:mysql /data1/mysql
chown -R mysql:mysql /data2/mysql
chown -R mysql:mysql /backup/mysql
### END OF SCRIPT ###
Sample Output
chmod 750 make_mnt_LV.sh
df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 4.0G 1.2G 2.7G 31% /
/dev/sda2 147G 189M 140G 1% /mnt
lvdisplay
No volume groups found
./make_mnt_LV.sh
Physical volume "/dev/sda2" successfully created
Volume group "vg" successfully created
Logical volume "myvmdisk1" created
mke2fs 1.35 (28-Feb-2004)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
3932160 inodes, 7864320 blocks
393216 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=8388608
240 block groups
32768 blocks per group, 32768 fragments per group
16384 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000
Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 32 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
Logical volume "myvmdisk2" created
mke2fs 1.35 (28-Feb-2004)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
3932160 inodes, 7864320 blocks
393216 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=8388608
240 block groups
32768 blocks per group, 32768 fragments per group
16384 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000
Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 28 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
Logical volume "myvmdisk3" created
mke2fs 1.35 (28-Feb-2004)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
3932160 inodes, 7864320 blocks
393216 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=8388608
240 block groups
32768 blocks per group, 32768 fragments per group
16384 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000
Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 29 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
--- Logical volume ---
LV Name /dev/vg/myvmdisk1
VG Name vg
LV UUID h10Ev4-EVYY-CoGl-2AHS-sjqe-BNHE-297EyT
LV Write Access read/write
LV Status available
# open 1
LV Size 30.00 GB
Current LE 7680
Segments 1
Allocation inherit
Read ahead sectors 0
Block device 253:0
--- Logical volume ---
LV Name /dev/vg/myvmdisk2
VG Name vg
LV UUID UM6GmA-s0vr-Mt6u-kh8m-wvMr-TMtD-rb34kk
LV Write Access read/write
LV Status available
# open 1
LV Size 30.00 GB
Current LE 7680
Segments 1
Allocation inherit
Read ahead sectors 0
Block device 253:1
--- Logical volume ---
LV Name /dev/vg/myvmdisk3
VG Name vg
LV UUID nCKCDh-MgIf-92il-FQHu-XduC-yJsO-koIGgM
LV Write Access read/write
LV Status available
# open 1
LV Size 30.00 GB
Current LE 7680
Segments 1
Allocation inherit
Read ahead sectors 0
Block device 253:2
df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 4.0G 1.2G 2.7G 31% /
/dev/mapper/vg-myvmdisk1
30G 77M 28G 1% /data1/mysql
/dev/mapper/vg-myvmdisk2
30G 77M 28G 1% /data2/mysql
/dev/mapper/vg-myvmdisk3
30G 77M 28G 1% /backup/mysql
Modifying your MySQL my.cnf to use the new data directories available.
http://dev.mysql.com/doc/refman/5.1/en/innodb-configuration.html
What do we have already?
grep "data" /etc/my.cnf
# mysql-data-dir/my.cnf to set server-specific options (in this
# installation this directory is /usr/local/mysql/data) or
#innodb_data_home_dir = /usr/local/mysql/data/
#innodb_data_file_path = ibdata1:10M:autoextend
#innodb_log_group_home_dir = /usr/local/mysql/data/
#innodb_log_arch_dir = /usr/local/mysql/data/
Make a backup and edit using your favourite text editor:
cp /etc/my.cnf /etc/my.cnf.old
vi /etc/my.cnf
Check again:
This setup will place one INNODB datafile on each of the newly created Logical Volumes.
An alternative would be to place the logfiles on one of them instead.
grep "data" /etc/my.cnf
# mysql-data-dir/my.cnf to set server-specific options (in this
# installation this directory is /usr/local/mysql/data) or
datadir=/data1/mysql/data
innodb_data_home_dir = /data1/mysql/data
innodb_data_file_path = /data1/mysql/data/ibdata1:10M:autoextend;/data2/mysql/data/ibdata2:10M:autoextend
innodb_log_group_home_dir = /data1/mysql/data
innodb_log_arch_dir = /data1/mysql/data
DBA Dojo 
a tiny mistakethe line before mount /dev/vg/myvmdisk1 /data1/mysqlshould be mkdir -p /data1/mysql