I have a linux server, and i want to make an image of the whole drive in real-time, like acronis does.
I use LVM religiously. It makes filesystem management so much easier...if you use lvm there's a tutorial here: http://www.howtoforge.com/linux_lvm_snapshots
LVM is a good choice.
LVM snapshot can be created in real time by -s when using lvcreate: http://fclose.com/p/linux/man/8-lvcreate/#lbAE
For example, we can create a 2GB snapshot of lv_root by:
Then we can dd the snapshot out (this cost time):