Ben Rockwood wrote: > This is just a thought exercise.... but I'm curious what would exactly be > involved in essentially biasing caching such that a 'ls -al' was never slow. > > In my experience, IO speed an vary, but if a user types "ls -al" in the shell > and the response isn't nearly instantaneous they start calling IT staff. > Being able to cache all that data (perhaps by priming it) ensuring its not > bumped out later would be interesting. > > For ZFS this is primarily a function of ZAP and DNLC, correct? Does > "metadata" caching satisfy everything a directory listing could want or are > there bits of data that slip through requiring actual disk IO? >
While not an extensive study, on a recent project I was working on, the default DNLC ended up being about 2 orders of magnitude too small. In the bad old days when memory was a precious, limited resource tuning down DNLC made sense. Today, I think we might be too small, by default. Fortunately, it is easy to change. -- richard
