Why can't we have two cache drives?

TrueNAS General
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(TrueNAS Scale) I have a question about using L2ARC as metadata only…why can’t there be two cache drives, one metadata, one for normal cache?

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Well, you can have multiple. They get striped.

Thus they share responsibility.

It doesn’t really make sense to separate it, it would just mean not being able to take advantage of the combined performance of two drives in either case.

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“Normal” cache (i.e, “all”) includes both userdata and metadata.

But that’s moot. Your “cache” is the ARC which lives in RAM. Simply doubling the physical RAM will do much more for performance than an NVMe L2ARC vdev.

Before committing to an L2ARC, diagnose why your performance is low, and gauge if the system is liberally and effectively making use of the ARC in the first place.