Is anyone using dm-cache with large SSD? By large I mean large in comparison to HDD size. something like 1TB MLC SSD caching 4TB or 8TB HDD. I wonder what’s performance of such setup comparing to native SSD.
I used 60GB cache for 2TB drive in the past but performance was quite miserable. Thus I wonder if 25% SSD size ratio would produce significantly better results.
The size of the cache is not really that important, it is the prediction that rules the world.
When the algorithm fails you end up reading and writing at the same time and tanking the HDD and SSD performance.
SSDs get away with it for the same reason as their predecessors - striping data across an array of slow drives. dm-cache would be interesting if the back-bone was some nested array like raid 10.
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