Eitan Adler wrote:
gjournal will replay all write attempts
(metadata and data) before the failure, so you should be relatively
sure that all writes are done correctly.
As I understand it journals work by writing to disk a log of all the
changes that have to be made - waits for confirmation that it wrote
the data - and then attempts to make those changes. If after the
confirmation there is a crash the log file is replayed.
Certain virtual machines will report to the OS that it wrote the data
to disk before it actually does so. In that case journaling doesn't
actually help as the log file is still not on some form of stable
storage.
I am not an expert on the subject, I thought the journal will replay all
logged write attempts and since the number of all write attempts logged
in the journal will be much bigger than the number of requests a cache
can hold you will be sure that all writes will be done on the
filesystem. Again, I am not an expert on the subject...
Nikos
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