# Today's `LSM`
+ Compare to the original `LSM`:
  + Multiple disk components can merge together 
  + No need to modify existing components 

+ `LSM` component can be any index structure
  + Memory component (concurrent data structure) 
    + `B+-Tree`
    + `skip-list`
  + Disk component
    + `B+-Tree`
    + `SSTables`
![`smart`](TodaysLSM_aa_001_20221021.png)

------------------------------------------------------------

Exploits the immutability of disk components to simplify the concurrency control and the recoveribility.