[MUD-Dev] Disk v. Mem

[clawrenc at cup.hp.com]

In <199705130518.TAA20541 at mail.pixi.com>, on 05/12/97 
   at 10:51 PM, "ashen" <ashen at pixi.com> said:

>what are the advantages of swapping out objects
>to disk as opposed to keeping them in memory?

Ease of recovery in case of a server or system crash.  If done right,
nothing is lost.  The game restarts in exactly the same state as it
went down in.  (Of course this can be a problem if its that state
which lead to the crash -- you get an endless cycle of
crash/restart/crash/restart/crash/restart...)

A truly persistant world where changes *ARE* permanent.  (Bubba drops
a stick in the town square?  That stick will be there for all eternity
until something comes along and explicitly (re)moves it)

Reduced memory consumption.  You want to really run in-memory when
your DB size is measured in Gigabytes?

Increased peformance:  You know more about your data handling
behaviours than the OS is ever going to know.  The OS swaps out pages. 
Your objects are not synonymous with pages.  You can do a much better
job.

>isn't it more costly in speed to write to disk? 

Yup.  That's why cacheing is so important.

>what kind of savings do you get versus this extra cost?

See above.

--
J C Lawrence                           Internet: claw at null.net
(Contractor)                           Internet: coder at ibm.net
---------------(*)               Internet: clawrenc at cup.hp.com
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