I am running a Postgres instance for a ~200GB database (including data and indexes). It's on a Google Compute Engine server. My options for disk are either network block storage or local SSD. I'm wondering if I can use local SSD as a caching layer for the database.
Network block storage is persistent but has relatively slow read/write and low IOPS. Local SSD has high throughput read/write and high IOPS, but is effectively transient and does not survive a shutdown of the instance.
I suppose I could run two Postgres instances: the master on network block storage, and a read-only copy on the local SSD. However, just like Linux automatically uses available ram as disk cache, I wonder if I can tell Linux to use the local SSD as a cache for the slower network block storage. Is anyone aware of how to go about that?