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--></style></head><body lang=EN-US link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt'>I want to use Tahoe-LAFS as the storage component of a network backup application. In this application, each node hosts a backup application as well as a full Tahoe node (storage server + client). The backup application can be used to back up data on the node to the Tahoe storage network. I have found a limitation of Tahoe-LAFS that makes it less than ideal for this type of application.</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:11.0pt'> </span><o:p></o:p></p><p class=MsoNormal><span style='font-size:11.0pt'>Here’s the issue:</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:11.0pt'>When you use Tahoe-LAFS with the introducer, every node is advertised as a potential storage node. This includes the local node which is also is hosting a Tahoe storage node. When the backup application is used to store local data to the Tahoe-LAFS network, it may end up putting a slice of the data on its own node. There are 2 problems with this:</span><o:p></o:p></p><ol style='margin-top:0in' start=1 type=1><li class=MsoListParagraph style='margin-left:0in;mso-list:l0 level1 lfo3'><span style='font-size:11.0pt'>It is wasteful of storage space</span><o:p></o:p></li></ol><p class=MsoNormal style='margin-left:1.0in'><span style='font-size:11.0pt'>The local node already has a copy of the data so storing a slice locally does not really improve resiliency.</span><o:p></o:p></p><ol style='margin-top:0in' start=2 type=1><li class=MsoListParagraph style='margin-left:0in;mso-list:l0 level1 lfo3'><span style='font-size:11.0pt'>It reduces resiliency</span><o:p></o:p></li></ol><p class=MsoNormal style='margin-left:1.0in'><span style='font-size:11.0pt'>If the hard drive fails on the node, Tahoe slice stored on it may be lost.</span><o:p></o:p></p><p class=MsoNormal style='margin-left:1.0in'><span style='font-size:11.0pt'> </span><o:p></o:p></p><p class=MsoNormal><span style='font-size:11.0pt'>I have discussed this issue with people on the tahoe-lafs IRC node and we came up with a proposal for a new feature which addresses this issue.</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:11.0pt'> </span><o:p></o:p></p><p class=MsoNormal><span style='font-size:11.0pt'>The proposed new feature is to create a new configuration flag for the Tahoe-LAFS client which prevents the client from storing data to its local storage node (“don’t_use_local_storage”). When the flag is set, the client gets the name of the local storage node from tahoe.cfg using the nickname attribute of the [node] section. When the client creates a list of storage nodes to store content to, it excludes this particular node from the list.</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:11.0pt'> </span><o:p></o:p></p><p class=MsoNormal><span style='font-size:11.0pt'>Make sense?</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:11.0pt'> </span><o:p></o:p></p><p class=MsoNormal><span style='font-size:11.0pt'> Bruce T</span><o:p></o:p></p></div></body></html>