2: Storage

Disks and Files

Explain why Storage is important for the Database

Explain the memory hierarchy.

1. CPU (with registers):

   • used for immediate instruction execution (sofortige Auftragsausführung)

2. (CPU) caches:

   • automatically store recently (zuletzt) used data

   • critical for performance because they reduce CPU stalls

3. main memory:

   • holds active programs and data

   • acts as the primary working area for the OS and DBMS

4. hard disks/SSDs:

   • microseconds for reads, slower for writes

   • used for persistent storage

5. tape library:

   • Used for backups and archival data

=> fast but small and expensive memory is close to the CPU

==> large but slow memory at the periphery

=> each layer cache (zwischenspeichern) the one below it

Explain difference between latency time and access time.

Latency = time until the first byte arrives → How long does it takes before the CPU can start using the data

Access time = latency + transer time

Name different capacity. Start with the smallest and end with the largests.

1. bytes

2. kilo-/megabytes

3. gogabytes

4. terabytes

5. petabytes