cleanup on hardware

lectures/file-and-data-systems/slides.qmd

@@ -60,8 +60,9 @@ Disk quotas for prj 30001639 (pid 30001639):
 ## Caching
 * Keeping data *in memory* for frequent re-use.
 * Usually storage media like disks have small caches with better properties.
-* e.g. HDD of 16 TB with a 512 MB of cache.
-* Operating systems also cache read.
+* e.g. HDD of 16 TB with a 512 MB of RAM cache.
+* Operating systems also cache reads.
+* Caching writes in RAM is trouble because of the risk of data loss due to power loss / system crash.
 
 # Hardware types 
 
@@ -78,7 +79,7 @@ Disk quotas for prj 30001639 (pid 30001639):
 
 
 * All figures based on a quick google search in 06/2024
-* RAM needs electricity to keep the data.
+* RAM needs electricity to keep the data (*volatile memory*).
 * All but tape usually remain powered in an HPC.
 
 ## RAM disk