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Unable to use zpool as "Secondary Storage" when cache is set to Primary. (6.12 rc7)

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It looks like this isn't supported, but is there any way to have the zpool act similar to vanilla Unraid array? 


Meaning in an Unraid array (not using zfs pools), in the share settings you can set the storage path from Cache to Array, or Array to Cache, etc..  But when the pool is ZFS, there's no option to go from Cache > Zpool.  This seems like a big drawback to me, as there's no advantage to using the cache disk for writes, unless the data is going to stay there. And there's no mover option available. This really makes me rethink my decision to use ZFS at all, as this was a great feature I was looking forward in moving to using Unraid OS for my storage needs.  Is this on the roadmap at all? 


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Well that makes the choice easy.  I thought I was giving up performance by using Unraid Array versus ZFS Pools and I am for the reads - but it's not as bad as I had thought reading from a single disk.  With 2.5Gb networking between my machine and Unraid box, I'm maxing out the link for READ and when writing to the cache it's max too.  But writing directly to the Unraid Array, is utter garbage after the first 5GB with no cache.  I think I'll stick with non-ZFS pools for now, but will still use the ZFS file system to get some of the added error handling.   


I wonder if there will be an option to migrate the Unraid array over to full ZFS Array in 6.13, or I'm stuck with what choices I make now - which isn't that bad.




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15 hours ago, yoleska said:

I wonder if there will be an option to migrate the Unraid array over to full ZFS Array in 6.13

As long as you have devices to create a new pool you can then use the mover to move the data, without the devices to create a new pool you'd need to backup the array data first before creating a pool and restore the data.

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  • 1 month later...

I have the same problem and same opinion. I bought 4x 8TB U.2 NVMe drives in order to  create a zfs pool, while I am using a a 1TB M.2 cache and separetly 4TB NVME as a single disk on array without parrity. So I am not interested at all in an array, since I need the full performance out of this server in file transfer. But as the yoleska wrote, it is not possible to have the combination of a zpool and cache as primary and secondary storage which is really disappointing after spending so much for my zfs pool. By the way, I cannot see in unblalance my zpool, in order to move data, I can see only the cache and array, despite re-installing the pluggin, which is also very disappointing. Without zfs is unraid useless in my opinion, its too slow compared to my proxmox and 2 x QNAP Server, despite a quite poweful machine with 12 core-cpu 64GB RAM. Furthermore, it is much complicated to get apps or dockers run how I want. I spent so much time in last 4 weeks for Unraid and it is still in construction. I dont have time, otherwise I would try TrueNas. 

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The cache drive concept exists because writes to the Unraid array are comparatively slow. When writing new files they can go to an SSD cache drive and then get copied over to the main array of spinning drives overnight when nobody cares how long it takes.


I'm curious what benefit you see of putting an M.2 cache drive in front of a ZFS pool of NVME drives. Direct writes to the ZFS pool are going to be very fast, putting a cache drive in front of that doesn't get you anything that I can see.

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