Disk mirroring

Shell Programming and Scripting
1

Good Morning :slight_smile:

I have a new challenge to solve, I am going to write a new backup disk mirroring script. The current one, whcih is useing 'dd' caused some stalled systems :frowning:
Currently I am in the phase of experimenting with different methods, I was thinking about dump/restore afio/cpio or rsync.
The best solution looks like rsync for me, but what os your opinion ?

The script will run 1 time a week and has to mirror the complete OS disk to a second 'backup' disk. Only the OS FS will be backed up, no data filesystems !
The backup will run on a live system, I cannot go down to sinle user mode and/or remount the FS readonly for backing up :frowning:

With 'dd' the Linux system will be forced to flush all dirty pages, which caused the stalled situation I described before. So I need a mirror method with doesn't cause a extremly high load, because the systems are high loaded anyway and is more or less fast; of course I could need hours for it, but it should be finished the next morning :slight_smile:

Thanks for all hints !

Btw, the systems are RH AS 2.1 systems, IA64 multi processor and big RAM. The disks are default SCSI disks (36 or 72 GB), primary and backup disks have a seperate controller each. The shell is free choosable, I thought on bash.

Cheers
malcom

2

dd would be my choice, but the disadvantage is that it is block level, so it has to copy blocks that have not changed.

Is this a boot disk, or a data disk? If it is data, I would use cpio -pdmv
This will not copy files that have not changed, saving I/O.

3

Hi,

it is the primary OS boot disk, and using dd on linux is a bit critical. The systems I wnt to mirror, are mostly NFS Fileservers. The dd command forces the linux system to flush all dirty pages, you can imagine what happens in that situation with the system :slight_smile: It stalls ...

Therefore, I can everything except dd :frowning: But dd was also my first idea, until this experience...

I already did some testings with rsync and it looks not so bad ..

4

I have been told you can do this, but have never tried (will try next week when I get back to the office)

# cat /dev/rdsk/c0t0d0s2 > /dev/rdsk/c1t1d0s2