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I know I can simply create a degraded raid array and copy the data to the other drive like this:

mdadm --create /dev/md0 --level=1 --raid-devices=2 missing /dev/sdb1

But I want the specific disk to keep the raw ext3 filesystem so I can still use it from FreeBSD. When using the command above the disk will be a raid disk and I can't do a mount /dev/sdb1 anymore.

A little background info. The drives in question are used as backup drives for a couple of Linux and FreeBSD servers. I am using the Ext3 filesystem to make sure I can quickly recover the data since both FreeBSD and Linux can read from that without problems.

If someone has a different solution for that (2 drives in raid 1 that are readable by FreeBSD and writeable by Linux), I'm open for suggestions.

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up vote 1 down vote accepted

I would suggest ZFS for your raid. It is native in the FreeBSD kernel (note: you need to make some kernel mods to make it work without kernel panics - basically increase the kernel memory), and there is a fuse module for Linux.

It is by far the most flexible RAID system I have ever come across.

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is the Linux ZFS performance decent these days? In the early days with the fuse module it wasn't usable imho. I know the FreeBSD version works just fine but I was still having doubts about the Linux version. But I'll give it a shot. – Wolph Mar 30 '11 at 23:07
I use it in a couple of production environments under Linux. While not as fast as FreeBSD it's perfectly usable. – Majenko Mar 30 '11 at 23:15
ok, I'll give it a try :) Thanks for the help. – Wolph Mar 31 '11 at 9:01

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