on disk and in memory

Hello,

If a table takes 100 MB while on disk, approximately how much space will it take in RAM/database buffer?
Context - We are designing a database that will hold a couple of GBs of data. We wanted to figure out how much shared_buffers we should provide to ensure that most of the time, all the data will be in memory. This is mostly master data (transactions will go to Casandra), and will be read from, rarely written to. We do need data integrity, transaction management, failover etc - hence PostgreSQL.

Regards,
Jayadevan

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