Device names is changed when a hard drive is moved to a other location in the machine or removed or by some reason it fails

Each device is given a name like hda1,hda2 etc(for IDE). or sda1,sda2 etc. (for SCSI) under /dev direcotry but when a hard drive is moved to a other location in the machine or removed or by some reason it fails, then other device names will be changed that results in invalid references to other devices. To overcome this problem, instead of referencing device name we can use UUID of the device which is always unquie number. For this we can use "devlabel" utility. To configure it follow the two simple steps:

1. Get the UUID of device(like /dev/sdc1)
# devlabel printid -d /dev/sdc1

Output:
P:6195eabc-4631-4ed8-9514-ed8cd4679ed0

2. Create a symbolic link which point to UUID. In this example "myHDD" is name given to symbolic link
#devlabel add -u P:6195eabc-4631-4ed8-9514-ed8cd4679ed0 -s /dev/myHDD

Output:
SYMLINK: /dev/myHDD -> /dev/sdc1
Added /dev/myHDD to /etc/sysconfig/devlabel

From this onward, you can use /dev/myHDD instead of /dev/sdc1. In some situation if /dev/sdc1 become /dev/sdc2 or /dev/sdc3, you need not worry because you are using /dev/myHDD which point to the actual HDD.

Good Read on Cloud Storage

blog.druvaa.com has a very good simple paper on " Cloud Storage". Visit The Dark Side of The Cloud".