Pavel Shtemenko published JFS recovering methodology. He suggested to use special utility JRescuer (even if you can't recover volume, you will save major part of files and directories structure)
JRescuer - is a product of eCo Software, (c) Pavel Shtemenko; The product is distributed through Mensys e-shop.
http://en.ecomstation.ru/showarticle.php?id=91
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