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<H1>[MUD-Dev] Persistant storage.... My current idea.</H1>
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<LI><em>To</em>: <A HREF="mailto:mud-dev#kanga,nu">mud-dev#kanga,nu</A></LI>
<LI><em>Subject</em>: [MUD-Dev] Persistant storage.... My current idea.</LI>
<LI><em>From</em>: J C Lawrence <<A HREF="mailto:claw#under,engr.sgi.com">claw#under,engr.sgi.com</A>></LI>
<LI><em>Date</em>: Wed, 22 Apr 1998 16:26:32 -0700</LI>
<LI><em>Delivery-date</em>: Wed Apr 22 16:26:52 1998</LI>
<LI><em>Delivery-date</em>: Wed, 22 Apr 1998 16:26:52 -0700</LI>
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<PRE>
Date: Sat, 4 Apr 1998 21:27:19 -0600
Message-Id: <199804050327.VAA08891#laurel,actlab.utexas.edu>
From: Cynbe ru Taren <cynbe#muq,org>
To: cg#ami-cg,GraySage.Edmonton.AB.CA
Subject: [MUD-Dev] Persistant storage.... My current idea.
cc: claw#under,engr.sgi.com
cg#ami-cg,GraySage.Edmonton.AB.CA (Chris Gray):
| If you keep an index table in memory all the time, then there will also
| be no more than one disk read to get any DB entry.
| [...] After a few header words, index file is an array of small
| structs, containing a 16 bit slot length, a 16 bit 'used' length, and
| a 32 bit file offset.
True, but if ram is cheap, why use disk-basing at all? :)
What's your average object size?
I presume your scheme works well with your design, but with many
systems, statistics show an average object size of 13-16 bytes.
E.g., Smalltalk-78 I believe quoted a value in this range; QwestMUCK
when I was running it was dominated by strings with a similar size;
I'm sure most Lisp system would show similar statistics.
Clearly, if the average object size on disk is 16 bytes, and the
index file is 8 bytes/entry as above and kept in memory, then the
disk db can be at most twice as large as the RAM image, which
isn't a very satisfying space gain for the all the coding effort
involved in implementing diskbasing.
The vm.t module I'm using in Muq currently has an in-ram overhead
of 1 bit per object on disk, which means that a system with the
typical average object size of 16 bytes can support a limiting
db 128x larger than process ram footprint in principle, and probably
a comfortable 10x factor in practice.
(I'm trying to set up Muq as a general-purpose server suitable for
a wide range of applications, so I have to make fairly conservative
design decisions on these sorts of issues. A more tightly targetted
server can of course make different trade-offs.)
Cynbe
--
J C Lawrence Internet: claw#null,net
(Contractor) Internet: coder#ibm,net
---------(*) Internet: claw#under,engr.sgi.com
...Honourary Member of Clan McFud -- Teamer's Avenging Monolith...
--
MUD-Dev: Advancing an unrealised future.
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<ul><li>Thread context:
<BLOCKQUOTE><UL>
<LI><STRONG>Re: [MUD-Dev] Persistant storage.... My current idea.</STRONG>, <EM>(continued)</EM>
<ul compact>
<ul compact>
<LI><strong><A NAME="00012" HREF="msg00012.html">Re: [MUD-Dev] Persistant storage.... My current idea.</A></strong>,
J C Lawrence <a href="mailto:claw#under,engr.sgi.com">claw#under,engr.sgi.com</a>, Sat 04 Apr 1998, 00:04 GMT
</LI>
</ul>
<LI><strong><A NAME="00018" HREF="msg00018.html">Re: [MUD-Dev] Persistant storage.... My current idea.</A></strong>,
Chris Gray <a href="mailto:cg#ami-cg,GraySage.Edmonton.AB.CA">cg#ami-cg,GraySage.Edmonton.AB.CA</a>, Sat 04 Apr 1998, 23:21 GMT
</LI>
<LI><strong><A NAME="00019" HREF="msg00019.html">Re: [MUD-Dev] Persistant storage.... My current idea.</A></strong>,
Chris Gray <a href="mailto:cg#ami-cg,GraySage.Edmonton.AB.CA">cg#ami-cg,GraySage.Edmonton.AB.CA</a>, Sat 04 Apr 1998, 23:21 GMT
<UL>
<LI><strong><A NAME="00022" HREF="msg00022.html">Re: [MUD-Dev] Persistant storage.... My current idea.</A></strong>,
Ben Greear <a href="mailto:greear#cyberhighway,net">greear#cyberhighway,net</a>, Sun 05 Apr 1998, 02:02 GMT
</LI>
</UL>
</LI>
<LI><strong><A NAME="00271" HREF="msg00271.html">[MUD-Dev] Persistant storage.... My current idea.</A></strong>,
J C Lawrence <a href="mailto:claw#under,engr.sgi.com">claw#under,engr.sgi.com</a>, Wed 22 Apr 1998, 23:26 GMT
</LI>
</ul>
</LI>
<LI><strong><A NAME="00004" HREF="msg00004.html">Re: [MUD-Dev] (fwd) Re: Roleplaying</A></strong>,
J C Lawrence <a href="mailto:claw#under,engr.sgi.com">claw#under,engr.sgi.com</a>, Wed 01 Apr 1998, 22:26 GMT
<LI><strong><A NAME="00002" HREF="msg00002.html">Re: [MUD-Dev] World Persistence, flat files v/s DB v/s ??</A></strong>,
J C Lawrence <a href="mailto:claw#under,engr.sgi.com">claw#under,engr.sgi.com</a>, Wed 01 Apr 1998, 19:41 GMT
<UL>
<li><Possible follow-up(s)><br>
<LI><strong><A NAME="00003" HREF="msg00003.html">Re: [MUD-Dev] World Persistence, flat files v/s DB v/s ??</A></strong>,
J C Lawrence <a href="mailto:claw#under,engr.sgi.com">claw#under,engr.sgi.com</a>, Wed 01 Apr 1998, 20:48 GMT
</LI>
<LI><strong><A NAME="00005" HREF="msg00005.html">Re: [MUD-Dev] World Persistence, flat files v/s DB v/s ??</A></strong>,
J C Lawrence <a href="mailto:claw#under,engr.sgi.com">claw#under,engr.sgi.com</a>, Wed 01 Apr 1998, 22:28 GMT
</LI>
</UL>
</LI>
</UL></BLOCKQUOTE>
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