Mac OS X - mirroring directories to other disk

Question

What I need is this:

1) choose some directories on one disk and have these directories mirrored on another disk automatically. For example: suppose I have a directory on diskA called /myFiles and the same directory on diskB. Now, every time I change something on diskA, the changes are echoed to diskB automatically. If I delete a file on diskA, the file is deleted from diskB and so one. A mirror.

Is there a way to have some deamon, service or whatever running on background that allows me to do that on Mac OS X Snow Leopard?

NOTE: I know about Time Machine and about rsync and other manual synchronization tools, but what I need is just some directories on one disk to another.

Answer 1

Rsync is just what you want, all you will find are rsync GUIs that are a lot less useful than the command line program you already have. Here are some guis - Arsync, backuplist+, dropsync, grsync, synctwofolders.

If Rsync isn't what you want, why?

Folder actions are a pretty easy thing to make, with limitations. You could use crontab every five minutes. Here's one such folder action.

Answer 2

I know you said "directories", but here is a way to do it with disks. I have the following setup running:

• Linux host A exports a local disk as iSCSI disk
• Linux host B exports a local disk as iSCSI disk

(those two disks are the same size)

• Mac OS X host mounts the two iSCSI disks with the GlobalSAN initiator, and I created a RAID1 volume on them.

Changes are written to both disks at once. The volume can be accessed when at least one iSCSI disk is present. Speed + latency is of course limited by the network.