Deffer Write - Average - adjustable load/independent load Topic is solved

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Deffer Write - Average - adjustable load/independent load

Post by cichy45 »

Hello all!

My setup: 2x SSD as L2 cache with Defer Write - Average option selected. Cached HDD: target 1/2 - new and fast Seagate SSHD, target 3 - older Seagate HDD, lower performance.

I observed, that when using Average Primocache writes to ALL HDD with same speed, for example 40 MB/s. My idea: option to adjust (or just hard coded into program) disk LOAD that Primocache should target (30%, 50%, 80%), and allow each single HDD to be monitored independently. So fast SSHD will be loaded to 50% and write at 100 MB/s, old slow HDD will also be loaded to 50% but write at 40 MB/s. Thanks to that independent monitoring, faster HDD will be able to quicker download data from L2 storage and whole process will not be slowed down by the slowest disk in cache pool.

Image so it is more clear. Target 1 and 2 (fast HDD) is writing same MB/s as slow Target 3 despite lower activity %, all because of high % activity on Target 3 (slow HDD). When all disks (slow and fast) would be allowed to get to 80% activity, fast HDD would finish flushing faster.
2021-01-01_214600.png (9.88 KiB) Viewed 265 times
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Re: Deffer Write - Average - adjustable load/independent load

Post by Support »

The writing speed of each volume depends on total amount to be written in this volume and latency. Each volume is independent and not limited by others. You may reduce latency to get a fast flush speed. Or you may create two cache tasks with different latency.
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