Can I Split a Mirror for Duplication?

Joined
Jul 25, 2018
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I've been testing FreeNAS on an old desktop for about a year, primary use is local file storage (documents, photos), local backup target for several client devices, as well as running a few plugins (obligatory Plex, still trying to work out Syncthing and Nextcloud). That desktop is running a single pool that consists of 1 vdev of 2 mirrored 6TB drives. Since that box has been working out so well I recently decided to pick up a thirdhand r510 to handle my FN needs, primarily because it's got 12x3.5" drive bays and ECC RAM. I figure I'll set the r510 up as the primary NAS and use the desktop FN box as a local backup (in the guest house) that only the other FN box can access for redundancy and an extra layer of protection against ransomware, fire et al (I have offsite backups, locals are just so much faster to restore).

I've played around with pools a bit, but am far from an expert. I've worked out how to resilver a degraded pool and it occurred to me I might be able to use this to create an initial clone of the current pool to set up the redundant FN system to save time running data over my network (and add a new drive to the box that's been running a year, reducing the likelihood of simultaneous HDD failure (I hope)). My plan is something like:

1. FNDesktop - Drives A1, A2
2. Buy 2 6TB drives, B1, B2
3. Remove A2 from FNDesktop, degrading the pool.
4. Install A2 to r510, import pool (data is located on A2, right?) in a degraded state
5. Install B1 to FNDesktop - replace A2 and resilver
6. Install B2 to r510 - replace A1 and resilver

Will this work, or am I missing something about pool configuration? My hope is that I'll wind up with two versions of the same pool on two boxes, each with a 1 year old HDD mirrored to a new HDD.

Alternately, some posts here helped me attach a third device to an existing mirrored vdev. If the above doesn't work like I hope it will, can I attach the new drives to the existing pool, resilver the drives across the mobo instead of the network, then remove the drives from the vdev and import them to the new machine?

If neither of those are a good way to accomplish mirroring a pool to a new box, I'd appreciate any suggestions or advice you have for me. Thanks for any help you can give, and for all the help I've already gleaned crawling through these forums. This stuff can feel pretty overwhelming, but you guys do a great job of explaining it in terms even I can process.
 

sretalla

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Your process will "work", but you need to watch out for the pool GUID... the clone of your pool will not know that the original lives on and vice versa, so if you try to bring that clone back to the original host, there will be issues deciding which copy is mounted and you will need to manually intervene (I suspect) to even mount one of them... probably no easy choice to mount both.

You may also find that you have issues to use replication tasks for that pool between the two systems.
 
Joined
Jul 25, 2018
Messages
4
@dlavigne I finally got around to trying it last night. Everything worked as expected.

@sretalla I hadn't thought of that, but it makes sense. I guess it's probably best I read up on snapshots and replication instead of trying to make up my own hacky solution.
 
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