More Notes on EC2 and LVM

Following up on my notes about running WordPressMU on EC2, I am still working on a clean implementation for setting up the disks on the EC2 m1.large instance the way I want. Once, I’ve made things work the way I want then I will go back and finish my other notes on running WordPressMU.

This is a collection of notes on what I think I want the disks to look like on first boot and reboot…

m1.large instances come with 850GB of disk space configured as:

• 850 GB instance storage (2 x 420 GB plus 10 GB root partition)
• /dev/sdb (/mnt on large and extra large instance types)
• /dev/sdc (on large and extra large instance types, not mounted)

I like the idea of creating a single large volume group on both physical disks, let’s call it “vgall” and then creating all of our logical volumes on that volume group:

• two database volumes (“lv_master”/”lv_slave”)
• one volume for back up (“lv_backup”)
• one volume for blog data (“lv_blogdata”)
• one swap volume (“lv_swap”)

Ok, so, we can’t create these logical volumes in the AMI setup, but we can create a script to run in rc.local that will set these up for us, and we can add these volumes to fstab to survive reboot.

So, our setupscript…

###  BEGIN OF SCRIPT ####!/bin/sh
#
# Script to make EC2 /mnt into a LVM volume

umount /mnt
pvcreate /dev/sdb /dev/sdc
vgcreate vg /dev/sdb /dev/sdc

lvcreate -L150G -n lv_master vg
mkfs -t ext3 /dev/vg/lv_master
mkdir -p /data/mysql_master
mount /dev/vg/lv_master /data/mysql_master

lvcreate -L150G -n lv_slave vg
mkfs -t ext3 /dev/vg/lv_slave
mkdir -p /data/mysql_slave
mount /dev/vg/lv_slave /data/mysql_slave

lvcreate -L150G -n lv_backup vg
mkfs -t ext3 /dev/vg/lv_backup
mkdir -p /data/mysql_backup
mount /dev/vg/lv_backup /data/mysql_backup

lvcreate -L150G -n lv_blogdata vg
mkfs -t ext3 /dev/vg/lv_blogdata
mkdir -p /data/blog-data
mount /dev/vg/lv_blogdata /data/blog-data

lvcreate -L140G -n lv_swap vg
mkswap /dev/vg/lv_swap
swapon /dev/vg/lv_swap

lvdisplay

mkdir -p /data/mysql_master/data
mkdir -p /data/mysql_slave/data

chown -R mysql:mysql /data/mysql_master
chown -R mysql:mysql /data/mysql_slave
chown -R mysql:mysql /data/mysql_backup
chown -R apache:apache /data/blog-data

### END OF SCRIPT ###

Our fstab:

# /etc/fstab
# modified to include lvm and swap

# original items
/dev/sda / ext3 defaults 1 1
none /proc proc defaults 0 0
none /sys sysfs defaults 0 0

# our LVM volumes and such
/dev/mapper/vg-lv_master /data/mysql_master ext3 defaults 0 0
/dev/mapper/vg-lv_slave /data/mysql_slave ext3 defaults 0 0
/dev/mapper/vg-lv_backup /data/mysql_backup ext3 defaults 0 0
/dev/mapper/vg-lv_blogdata /data/www ext3 defaults 0 0
/dev/mapper/vg-lv_swap / swap defaults 0 0

Some supporting notes:

• LVM can’t be set up and included in an AMI, so you need to write a script to set up the Volume groups and the logical volumes and run it in rc.local (Notes here)

• Notes on fstab – Take note of the comment on running swap on an LVM managed disk.

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