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Disk mirroring

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# 1  
Disk mirroring

Good Morning Smilie

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 Smilie
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 Smilie

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 Smilie

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.

# 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  

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 Smilie It stalls ...

Therefore, I can everything except dd Smilie 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

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