How many SSD is recommended to use when trying to increase the performance? how about the size of the SSD?

Problem/Symptom

How many SSD is recommended to use when trying to increase the performance? how about the size of the SSD?

Solution

In our mechanism of SSD cache, the maximum quantity is 8 SSD. But how many SSD will the customer need to use for best performance? This would depend on how much of the hot data size is. If read cache is used the capacity of all SSD in cache pool is summed up. If read-write cache is used then each SSD in the cache pool must have pair for mirroring and therefore pool capacity is half of summed up SSD’s size.
Mechanism of SSD cache tries to spread I/O across all SSD in the cache pool. So overall performance with multiple SSD in the pool is better then case of single SSD with greater size.
If the SSD cache is running out which means it is the full of the hot data, and this will also affect overall performance, the performance would be lower than disable SSD cache at that moment.
There is one thing need to reminder, it would require at least 8GB system memory to enable the SSD cache function.
More details regarding SSD cache functionality can be found in SSD Cache 2.0 White Paper.

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