Cache pools - 1tb NVME Gen3 and 1tb NVME gen 4

[qal1h]

This is my plan for two sets of cache pools:

1. I want to use my 1tb WD SN750(gen 3) and a second one, potentially the 1tb SN770 (gen 4) - would this work for caching? I understand the slowest read/write will be used when combined in RAID1 as a cache pool in Unraid. I guess the plan is to use the cache pool for appdata and docker/vm stuff. The gen 4 drive is at a reasonable price whilst the gen 3 drives isnt available anywhere.
2. A second set of sata SSD 2.5" drives for another cache pool for downloads a ADATA 960GB and 1TB Samsung 850 pro SSD - again RAID 1 cache pool for downloads.

Non conventional but could this work practically speaking?

[qal1h]

I asked chatgt

 

Yes, your plan for using two sets of cache pools in Unraid should work practically, though there are some considerations to keep in mind.

 

1. NVMe Cache Pool

Drives:
- WD SN750 (1TB, Gen 3)
- WD SN770 (1TB, Gen 4)

Usage:
- Appdata
- Docker
- VMs

Considerations:
- RAID 1 Performance: When combining these two NVMe drives in a RAID 1 configuration, Unraid will default to the speed of the slower drive for reads and writes. In this case, the performance will be limited by the Gen 3 WD SN750.
- Compatibility: Both drives will work together in a RAID 1 pool without issues, as Unraid does not require both drives to be of the same generation or speed. The capacity will be equal to the size of the smallest drive (1TB in this case).
- Practical Performance: Despite the SN770 being a Gen 4 drive, its benefits won't be fully utilized in this RAID 1 setup due to the SN750 limiting the overall speed. However, the SN770 should still work without problems.

 

2. SATA SSD Cache Pool
Drives:
- ADATA 960GB SSD
- Samsung 850 Pro 1TB SSD

Usage:
- Downloads

Considerations:
- RAID 1 Performance: Similar to the NVMe setup, the RAID 1 pool will operate at the speed of the slower drive. Here, the difference in capacity is minimal (960GB vs 1TB), and performance will be dictated by the slower SSD.
- Compatibility: These drives will also work together in a RAID 1 configuration. The usable capacity of the RAID 1 pool will be equal to the size of the smallest drive (960GB in this case).

 

Practical Considerations

- Redundancy and Performance: RAID 1 provides redundancy but not a performance boost for write operations. Read operations can benefit if Unraid can read from both drives simultaneously.
- Management and Maintenance: Managing multiple cache pools in Unraid is straightforward but requires proper configuration. Ensure that your appdata, Docker, and VM configurations point to the correct cache pool.
- Drive Wear Leveling: Different SSDs may have varying wear-leveling mechanisms and endurance ratings. Monitor the health of your SSDs regularly, especially since they're used for intensive tasks like appdata, Docker, VMs, and downloads.

 

Conclusion

Your setup is unconventional but should work fine in practice. Using different generations and types of SSDs in separate cache pools in Unraid will provide the redundancy and capacity you need for your specific use cases. Just be aware that the overall performance will be governed by the slower drives in each RAID 1 setup.