Hello everyone!
I have a laptop running slackware-current. The disk is /dev/sda and the root 'sda1' is xfs formatted (there is also linux swap at sda2).

recently I was trying to setup openvpn and had to copy a folder with configuration files from /usr/doc/openvpn_<version>/easy-rsa to /etc/openvpn.

I am sure the copying completed cause I got a prompt,
but a few seconds later the battery died on me. When I got mains and powered it up, I could see the directory I copied under /etc/openvpn, and the files where all there too. but they all contained nothing. i.e. they had a size of 0.

I read http://xfs.org/index.php/XFS_FAQ#Q:_..._filesystem.3Fhttp://xfs.org/index.php/XFS_FAQ#Q:_..._filesystem.3Fthat an external journal filesystem for root is not supported. I am not sure If it applies to my situation though. As in does it use an internal journal instead?

and the bottom line is: shouldn't the copying have completed successfully? shouldn't I be worried, that this copy failed?

Thank you for your help!

Sorry, but this is a risk you take by using XFS. The files you copy are not written right away, like with many filesystems (though not with the ext4 default either), instead they are kept in RAM and written later. There might be an option somewhere to make it safer ... not sure.

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The rap on xfs has always been that it does not handle hard shutdowns gracefully, i.e. you often get data loss or data corruption when you have a hard shutdown of an xfs filesystem.
Just because you got to a prompt before the system went down does not necessarily mean all the data was successfully written to disk; it probably had not been flushed out of ram or the disk buffers and written to disk before the shutdown occurred.

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If you keep reading the FAQ, you'll see something that applies to what you saw. (The next few FAQ entries also address your problem to some degree.)

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It does say so, however, it didn't talk about a remedy at all.
at any rate I used this guide to choose a filesystem and i'll live with it for now
with its goods and bads

Yeah, I mean it's a great high performance filesystem, with some drawbacks. Each filesystem has pros and cons like you said, this is one of the cons of XFS, so plan ahead for it.

I suspect you are using this on a laptop (battery went dead), I would have used JFS, it uses less CPU usage, is just as fast, and does not have this issue, but may have others

yes thats what happened..
JFS seemed... slow and I had not tried XFS in any other slackmachine so far.
and the laptop is old so I decided not to go for JFS.

I would like to see your views on filesystems for laptop, desktop, server, and router machines. can we make a poll out of this?

You can start a poll in the right forum for what filesystem they use ...

I think that laptops may be the exception, because: 1) They have batteries that can go out. 2) Because they have batteries, CPU usage is important. Thus I would conclude JFS is the best for laptops. For desktops, especially with a good UPS, you can probably safely use XFS.