[Info-vax] OS implementation languages

[David Jones]

Historically, every file-intensive application running under Unix got the benefit the system's
buffer cache without explicit tuning done by the programmer. The similar mechanism under
VMS, the virtual file cache, wasn't wasn't added until much later after VMS's reputation for
abysmal I/O performance was firmly entrenched. With the VFC in place, I/O performance is
now merely poor.

For SQLite, my VFS (Virtual File System) module uses RMS, but opens the file with the user
I/O option -- reads and writes are done with SYS$QIO. The VFS implements it's own buffer
cache as well. Since the VFS only gets what spills out of SQLite's own page cache, the VFS
cache doesn't show much effect with my benchmark program until sized to 8 Mbyte or so 
(~1.75:1 speedup with spinning rust,  1.25:1 with solid state).