ZFS Mirror Raid with external HDDs

[SDK Chan]

I have two questions regarding external mirror RAIDs.

1. Can I mount/unmount a external mirror RAID while the OS is running, safely without corrupting the pool ?
I think I read that putting a pool offline is not a good idea if both underlying devices are online.
But the last time I tried something like that, I corrupted the pool by accident so, I wonder how it could be done without corrupting the pool.

2. Let us suppose I reinstall the OS for whatever reasons, unlike UFS can I just mount the external HDD mirror, create a pool, and put the two HDDs inside without loosing data ?
Or do I always need to export a pool first, before reinstalling the OS ?
I read that if creating a new pool, the underlying devices will loose its data, but I wonder if the pool data is stored on the Mirror or somewhere in the OS.

 

[cracauer@]

Are you talking about ZFS mirrors?

But yes it's all safe.

 

[mer]

It sounds like on the external devices it's your user data, not the OS?
If I'm doing an install of new OS, I tend to export the user data and then import it after the base os is completed.

 

[SDK Chan]

Sorry for the late reply.
On the external devices is only user data.
What I actually mean is if my SSD for whatever reasons breaks, and I cannot boot anymore so, I replace it.
Then if I install FreeBSD anew can I still get access to the HDD ZFS RAID mirror, without exporting ?

 

[cracauer@]

Sorry for the late reply.
On the external devices is only user data.
What I actually mean is if my SSD for whatever reasons breaks, and I cannot boot anymore so, I replace it.
Then if I install FreeBSD anew can I still get access to the HDD ZFS RAID mirror, without exporting ?

Yes, you just use `import -f`` if the ZFS filesystem has not been exported before the OS change.