Author: toad
Date: 2008-04-08 14:26:46 +0000 (Tue, 08 Apr 2008)
New Revision: 19073
Modified:
trunk/freenet/src/freenet/client/FECCodec.java
Log:
Explain the alchemy
Modified: trunk/freenet/src/freenet/client/FECCodec.java
===================================================================
--- trunk/freenet/src/freenet/client/FECCodec.java 2008-04-08 14:19:00 UTC
(rev 19072)
+++ trunk/freenet/src/freenet/client/FECCodec.java 2008-04-08 14:26:46 UTC
(rev 19073)
@@ -65,6 +65,15 @@
if(splitfileType == Metadata.SPLITFILE_NONREDUNDANT)
return null;
if(splitfileType == Metadata.SPLITFILE_ONION_STANDARD) {
+ /**
+ * ALCHEMY: What we do know is that redundancy by FEC
is much more efficient than
+ * redundancy by simply duplicating blocks, for obvious
reasons (see e.g. Wuala). But
+ * we have to have some redundancy at the duplicating
blocks level because we do use
+ * some keys directly etc: we store an insert in 3
nodes. We also cache it on 20 nodes,
+ * but generally the key will fall out of the caches
within days. So long term, it's 3.
+ * Multiplied by 2 here, makes 6. Used to be 1.5 * 3 =
4.5. Wuala uses 5, but that's
+ * all FEC.
+ */
int checkBlocks = dataBlocks;
if(dataBlocks == 128) checkBlocks--; // Stay within the
8-bit code range, speeds things up 4x
return StandardOnionFECCodec.getInstance(dataBlocks,
checkBlocks, executor);
