cross-posted from: lemmy.ml/post/24330141
Hi there,
I’m not an expert in ZFS (I know enough to be a dangerous fanboy, haha), but I have an unraid server with two ZFS pools: one with HDDs and one with SSDs.
I recently bought a new 4TB Samsung 990 Pro SSD and want to add it to the SSD pool.
My initial thought was to add the 990 to the pool as a new VDEV. However, I’m also considering recreating the SSD pool with two drives in a strip configuration. I don’t mind disk failures because I regularly snapshot and back up the SSD pool to the HDD pool.
The main goal is to have access to all 5TB of storage.
I’m wondering if it’s a good idea to combine these drives into one pool or if it would be better to create three separate pools.
thundermoose@lemmy.world 2 weeks ago
Losing one drive in a striped pool with no redundancy means the entire pool is shot. Restoration from your HDDs may take a very long time, on top of data loss between the time of failure and your last snapshot. Striping without redundancy is fast, but dangerous.
This may work at first, and maybe you really do have a use case where this kind of failure is tolerable. However, in my experience, data is precious more often than it isn’t. Over time, you’re more likely to find use cases where the loss of the pool will be frustrating at best, and devastating at worst.
If you’re not using any redundancy, I would create separate pools so each drive can fail independently. You’ll have all 5TB of storage, but not contiguously. That at least constrains the failure modes you’re likely to run into.
If you are striping with redundancy (e.g., RAID-Z1), which I would highly recommend, you can lose a drive and not lose any data. That would take at least 3 equally-sized drives though, and you’d only be able to use the capacity of 2 of them.
thundermoose@lemmy.world 2 weeks ago
Oh, forgot to mention: striping in ZFS will use the capacity of the smallest drive. It sounds like you have a 1TB drive and a 4TB drive, so striping would give you access to 2TB at most.