Thank you very much :)

Regards
Mikael Liljeroth


2012/7/16 Tino Reichardt <list-jfs@mcmilk.de>
* Mikael Liljeroth <mikael.liljeroth@gmail.com> wrote:
> Thanks for the answer.
>
> I'm sorry I should have been more precise. In my case the files are more
> than a couple of days old and they are not the last modified on the system,
> is this still the desired behaviour?

Yes, if you have more than adequate RAM on that machine, it is possible,
that the pages were not flushed to disk, before some outage :(

You can flush all current fs cache via sync(8). Also most RAM of the
page cache can be flushed on linux also. Here is a goot drescription of
this: http://linux-mm.org/Drop_Caches

> Do you mean that the order and time the log records are written to disk
> could not be the reason why my files have been truncated? Just out of
> curiousity, where can I find information on what exactly the order and
> timing of log records disk writes depend on? I read in this (

This is very difficult to analyse. It may be restoreable via the
difference of the pmap[] and wmap[] tables of the dmap structure,
which is a part of the allocation bitmap.

I have a tool, which can dump the content of the two bitmaps, so you can
get the difference of the two. And of cause, there may be some data
which was partly written.

> I do not need a ponies flag, just something to improve the situation a
> little. I would be willing to accept that files were truncated, but not
> files that are more than a couple of hours old. The best solution for me
> would be something without having to modify the source of my own
> applications if possible. Patching the kernel or jfsutils or modifying some
> parameter would be better for my particular situation.
>
> Regarding the fsync approach, would it be possible to do this system wide
> or does it have to be the process holding the filedescriptor to that
> particular file? I'm thinking something like a separate process with a
> timer that issues a fsync every 10 min or so?

crate a cronjob, which does a sync:

# mkdir /etc/cron.minute
# echo '*/1 * * * * /usr/sbin/run-cron /etc/cron.minute' \
  > /var/spool/cron/root  (or: cronatb -e)
# echo sync > /etc/cron.minute/do-a-sync
# chmod +x /etc/cron.minute/do-a-sync


The prog is available here, but only pmap is dumped, you have to modify
it a bit: http://www.mcmilk.de/projects/frisbee-ng/dl/ ...
If you need help with the bitmap dump tool (fng-info), just send another
mail to this list.

Good luck.

--
regards, TR

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