【Join Our Co-creative Technological Solutions Discussion】About Accelerating HDD With SSD Context

Operating System ZimaOS
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【Join Our Co-creative Technological Solutions Discussion】About Accelerating HDD With SSD Context

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Another survey regarding accelerating HDD with SSD Context:

Some user has a spare SSD/NVME but does not neccessary need to store anything on it. A good use of this spare SSD/NVME we are looking into, is to use it to accelerate any mechanical HDD in the box. Additionally, having a cache layer potentially gives HDD more relief by being able to sleep longer (a bit).

Questions:

  • How interested are you about this idea? 1 (least) to 10 (most)

  • Do you have a preferred cache tool (e.g. FlashCache, EnhanceIO, dm-cache, Bcache)? Why is it?

  • How long have you been using this technique to accelerate?

  • Is ability to toggle it ON and OFF critical? Or leave it ON behind the scene all the time?

3 Likes
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2

I give it a 10 on my scale since it gives me an easy way to use the PCIe SSD card that I recieved as part of my kit.

Interested in any method that works and can be implemented easily, even in CLI.

I don’t see any reason for a toggle but…

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1. How interested are you in this idea? (1–10)
Answer:
I would rate it 9/10.
In setups using MergerFS + SnapRAID, SSD caching is especially valuable because SnapRAID does not provide real-time performance improvements and MergerFS itself has no built-in caching layer. An additional cache layer can significantly improve responsiveness.

2. Do you have a preferred cache tool? Why?
Answer:
For my use case, bcache or dm-cache would be the most suitable options.

  • bcache is very flexible and well-suited for read/write caching

  • dm-cache is stable and tightly integrated via the Linux device mapper

What matters most to me:

  • Support for write-back and write-through modes

  • Proper compatibility with MergerFS (no data inconsistency issues)

  • Safe interaction with SnapRAID (cache must be flushable before sync)

Nice-to-have features:

  • Per-folder or per-share caching policies

3. How long have you been using this technique?
Answer:
I’ve been using SSD caching for over a year across different NAS setups.
It makes a noticeable difference, especially with mixed workloads and many small files.

4. Is it important to be able to turn it on/off?
Answer:
Yes, absolutely critical.

In a SnapRAID-based setup, it’s important that:

  • the cache can be fully flushed before running a sync

  • caching can be temporarily disabled (e.g., for maintenance or debugging)

Ideally, the system should provide:

  • A simple on/off toggle in the UI

  • Visibility into cache stats (hit rate, usage, write-back queue)

  • A “safe mode” (write-through) option for maximum data integrity

Optional feedback / feature requests:

  • Native integration into the ZimaOS Storage Manager (similar to Merge Storage)

  • Support for multiple SSDs as a cache pool (even with mixed sizes)

  • Ability to define multi-tier caching (e.g., NVMe + SATA SSD)

  • Robust handling of reboots / power loss (no data loss in write-back mode)

4

Crudely use this technique manually with a 512gb NVME, eg “fast cache” move files in and out through the fast cache, saves me time if storing large files. A form of acceleration would be great, leaving it on would be just a nice simple benefit in keeping with the design philosophy of Zimaos, the last thing I need is another “tuning” tool, but just something that works would be brilliant. 10

5

Sounds interesting, and it would be good to improve the network file copy throughput. What happens in the event of an unscheduled power outage (no UPS on my system)?
Would this be limited to non-OS storage and could one SSD/NVMe be used for ‘caching’ multiple RAID arrays?