> Hi, I have a problem with my JFS partition and I have a couple
> of questions. After an unclean unmount and a restart a couple
> of files have been truncated to size 0.

In virtually every case that is desired behavior, it is not a
problem.

> What could be the reason for these 0 sized files? [ ... ]

O_PONIES. http://lwn.net/Articles/351422/

> What I don't understand is when and in what order the log
> records are written to disk.

That depends, and does not matter.

> Is there any way of preventing this from happening in the
> future.

Setting 'hdparm -W 0' and mounting with '-o sync' is the only
safe way, with any filesystem type.

Otherwise there are varying degrees of lower safety, such as
modifying the applications you use to 'fsync' at the right
times, or changing page cache flusher parameters.

Whether people like it or not there is a (really huge) tradeoff
between throughput and latency/safety as to how often writes are
flushed to disk.

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