I'm experimenting with creating a software RAID 0 device from 4 EBS volumes on Ubuntu 9.10 running at Amazon AWS following this guide:
http://alestic.com/2009/06/ec2-ebs-raid
The device appears (and according to SysBench is 3.5x faster than a regular attached EBS volume).
Problem is, when I reboot the instance, all files on the RAID device are gone. The device is available and mounted where expected, but contains no files. I am able to write new files to it, which survive until the next reboot.
EDIT:
Here's the script I use to setup the RAID. It writes to /etc/fstab and /etc/mdadm.conf
#!/bin/bash
# Create RAID
volumes=4
devices="/dev/sdj /dev/sdk /dev/sdl /dev/sdm"
devicearray=($devices)
volumeids="vol-11111111 vol-22222222 vol-33333333 vol-44444444"
yes | sudo mdadm \
--create /dev/md0 \
--level 0 \
--metadata=1.1 \
--raid-devices $volumes \
$devices
echo DEVICE $devices | sudo tee /etc/mdadm.conf
sudo mdadm --detail --scan | sudo tee -a /etc/mdadm.conf
sudo mkfs.xfs /dev/md0
mountpoint=/mnt/raid
echo "/dev/md0 $mountpoint xfs noatime 0 0" | sudo tee -a /etc/fstab
sudo mkdir $mountpoint
sudo mount $mountpoint
/etc/fstab
# /etc/fstab: static file system information.
# <file system> <mount point> <type> <options> <dump> <pass>
proc /proc proc defaults 0 0
/dev/sda1 / ext3 defaults 0 0
/dev/sdb /mnt ext3 defaults 0 0
/dev/md0 /mnt/raid xfs noatime 0 0
/etc/mdadm.conf
DEVICE /dev/sdj /dev/sdk /dev/sdl /dev/sdm
ARRAY /dev/md0 level=raid0 num-devices=4 metadata=01.01 name=ip-10-194-5-235:0 UUID=67392a94:553fddec:4bc8e5c7:8d25c3ca