Cache pool with redundancy questions

7 posts in this topic



From what little information I could find it is possible to have a cache pool in RAID 1, correct?

I'm just not comfortable yet with just putting my VM's on an array with a delayed parity checks so I would like protection.

Now I'm trying to decide to go with unRAID if I can get "instant" redundancy in the cache pool.


So I found reasonably priced Intel 600P 1TB nvme ssd's (yes not the fastest I know but I don't want to exaggerate in price)


I'm open to buying 4 to get them to work in RAID 10 if such a thing is possible, meaning I would have 2TB cache.


So I have these questions:

  • RAID 1 cache pool?
  • RAID 10 cache pool?
  • If the previous applies: RAID 1 to RAID 10 conversion possible?


Thank you!


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17 hours ago, trurl said:

See the Cache Pool topics in the FAQ here


Thanks, somehow it did not show up in my search results.

Just out of curiosity, why is this not in the wiki? In a lot of pages it says that it's outdated so it's a bit difficult to find the right information when the wiki shows up first :(

I also get a download request when I try to search on the wiki itself :(


3 hours ago, thaddeussmith said:

You could always do hardware raid and assign that virtual disk to the cache slot.


Yes that was also an idea I was thinking about, but everyone speaks of extra SATA ports and disabling RAID.

Which is of course the primary idea of unRAID but I can't find a compatibility list with supported RAID cards (in RAID functionality), can you point me in the right direction please?


I did see a video of Linus Tech Tips saying that the RAID cards don't provide smart & status info, unless this has been added / fixed or can be provided in another way?

LSI SAS 9211-8i HBA or LSI SAS 9211-4i seem like good options if it's supported.



Thanks for answering my questions :)



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I use a LSI 9211-8i to support the array itself. My cache is for cache and docker configs only so I don't care about data resiliency, smart status, etc..  I didn't find any essential benefit to using the integrated btrfs pool and since I only had two disks I didn't like the reduced capacity either. I had a spare Megaraid 9261-8i laying around that doesn't support being flashed to IT mode, so I just run my cache drives on it with RAID 0 and present that virtual disk. Extra capacity, speed, and ease of use. If a drive fails I just replace and restore docker configs from backup.


Dunno if that answers your question since we obviously have different use cases and expectations for the cache storage, but it at least shows what is technically possible.


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Unraid doesn't see the underlying disks.. just a single virtual disk.




I don't know how to answer your support question with any sort of confidence. Work with the supported card list in the wiki and go from there. The 9211 is a known functional card in IT mode and a common recommendation for replacing the now problematic supermicro cards. You'll just have to try it.


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