What is HANA APPLIANCE:
Hana appliance is a combination of SAP Hana database software and the Hardware specification.
As you see above A SPA HANA Database has CPU , Main memory (Ram) and then the persistance layer i.e the disk containing the log volumes and Data volumes.
RAM is physical memory – 128GB is minimum needed for SAP HANA, 256GB,512 GB,1TB
Data volumes should be 3-4 times of RAM
Log volumes should be equal to RAM size.
Data is stored in RAM in two types of data store- Row Store and Column Store.
Row Store –as you know traditional databases store data in row store residing in disk, where as in HANA all row store data are stored in RAM.
Cloumn store- this data is stored in columns as in BWA.
What is Persistance Layer: data is memory is volatile, i.e in case of power loss or server crashes, the data in the memory is lost. Hence We need a persistance layer containing the data volumes and log volumes in the disk. SAP HANA has a save point parameter where in every 300 seconds the changes done
In traditional database- only data is fetched from database and all calculation and analysis is done in application server and then sent to frontend.
Where as in SAP HANA the data is fetched and calculated and analyzed and then sent to application layer making is very fast.