How do I force L2 cache to constantly clear out to my disk? Topic is solved

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trafgals
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How do I force L2 cache to constantly clear out to my disk?

Post by trafgals »

I have a Windows Storage Spaces parity setup (4x 16TB drives, 1 is parity). Read performance is very good on the Parity space and doesn't need to be cached, but writes are slow. So I've set up 500GB of NVMe SSD to act as a cache, as per:
220114v2_l2stuck.png
220114v2_l2stuck.png (145.78 KiB) Viewed 459 times
Initial tests have extremely good performance! So I'm super happy with this and am about to buy a licence.
However, I don't want the 'write cache' to just sit around - I want it to empty wherever possible into the Parity space (preferably until 100% free), and I want this activity to start at any time. My intent is for Primocache to act as an ongoing buffer, via my SSD card, to compensate for the slow writes only. Given that the NVMe doesn't have any redundancy, whenever the computer is on, I want Primocache to be writing into the Parity space, as holding data in the NVMe is a liability.

I've tried my best to set it up to achieve this, including with the 'Defer Write mode: Idle-Flush', but instead as you can see in the picture, the cache fills up, and stays full until about the 80% mark. It then sits there, staying full, even when the system is idle.

How can I have the cache continuously write to my slow underlying drive, so it's always ready for new data?
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Re: How do I force L2 cache to constantly clear out to my disk?

Post by Support »

You have misunderstood "Unused Cache". Please see the following document.
https://kb.romexsoftware.com/en-us/2-pr ... g-released

With Defer-Write enabled, you can check "Deferred Blocks" to know how much space is currently occupied by Deferred write-data, and the remaining space is free to cache new incoming write-data.
trafgals
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Re: How do I force L2 cache to constantly clear out to my disk?

Post by trafgals »

That answers my question, thank you. I'll be buying your product shortly. Kudos for such a great piece of software!
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