thanks, warren [ love your dot_com, btw ] ---

Warren Block wrote:
On Wed, 8 Apr 2009, spellberg_robert wrote:

howdy, y'all ---

so, i was looking over the offerings of the on_line retailing "usual suspects",
 when i got to thinking:

 q:  to what extent does freebsd cache recently_used hard_drive files ?

To the extent that RAM is available.

 q:  under freebsd, to what extent are
hard_drive internal_caches and their sizes [ e. g., 2mb, 8mb, 16mb ]
       important ?

It depends on workload.

i am not so much looking for a history_ and theory_of_operation as
 i am looking for a "yes/no" to the question:

q: should i pay up for hd_cache, if the other hd parameters are the same ?

Again, depends on workload. Also the difference in price for relatively small differences in cache RAM on the hard drive.

now that i have a handle on today's prices,
  the choice of retailer is very important.

it also appears [ from my reading of manufacturer's literature ] that
  the hd internal_cache is used as a write_buffer
  for the benefit of the chip_set,
  then the drive can take its own sweet time writing to its notion of "sector"s.

  for a mobo that is stuffed_to_the_gills with ram
  [ relative to the apps that it is running ],
  if i read you correctly,
  then reads will tend to come from mobo_ram and
  the hd_cache is mostly a write_buffer.
i suspect that the hd_cache would be more important for
  an os that doesn't do its own caching
  [ until its notion of "idle"ness occurs ].

something else that i just thought up while typing this:

 q:  are hd internal_caches non_volatile ?


not surprised.

id est,

 q:  do the cache contents survive a power_cycle ?

No.  You may want to look at SSDs.


[ some supplementary "fyi"s:

   yes, i am aware that
     hd access_times are a relative "eternity" to a chip_set's hd_port.

   i am not thinking about ram_size and swap_size and "thrashing";
     all of my boxen have plenty of ram.

   i know i have to read it in the first time.
   rather, i am thinking about opening and reading
     some file that i recently wrote and closed.

FreeBSD is pretty good at that. For example, reboot and start Firefox. Then close it and start it again.


There may be ways of prioritizing what's kept in cache, although I don't know them.

not important.
thanks for the thought, though.

to summarize,
  it looks like, for freebsd, i should
  "get a good price from a reputable retailer
  on a high_quality product from a reputable manufacturer".
then, i can save my worrying_time for really important subjects, like
  "the determination of the correct yardarm height for the hanging of pirates".

-Warren Block * Rapid City, South Dakota USA

nice part of the country, that.
chicago & north western territory.

mchenry county, illinois

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