Journals and jscan

Matthew Dillon dillon at
Tue Jan 16 10:53:16 PST 2007

:> 	I have at last got two DragonFly boxes up and it seems like a good
:> idea to get some data security with jscan based mirrors.

    I don't think it's production ready for that sort of thing.  The main
    problem is that the link represents a choke point and reduces filesystem
    performance greatly.  A second issue is that a frontend has to be
    written to reconnect and restart the journaling stream when the
    connection is lost and to deal long term connection failures (i.e. if
    one of the boxes is brought down).
:	Just to follow up - I had a play while I was waiting :) I hit a
:problem which may be a bug (or may be me) - I tried this:
:#mkdir /home/journal_test
:#cd /home/journal_test
:#cpdup /tmp tmp
:#cd tmp
:#mountctl -a /tmp:test | jscan -m stdin
:	I got this response pretty quickly:
:/tmp:test added
:Bad path: /vi.recover/vi.fH1xrt
:Bad path: /vi.recover/vi.fH1xrt
:Bad path: /vi.recover/vi.fH1xrt

    Hmm.  The path shouldn't be absolute.  Try using the -D option to 
    jscan to specify the base directory for mirroring operations.

    ... | jscan -m stdin -D /home/hournal_test/tmp

    Mirroring that way should mostly work.  It is fairly easy to debug
    issues that pop up by also using the -d option to generate human
    readable debug output.

					Matthew Dillon 
					<dillon at>

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