Data loss

xintron · 2010-10-14 06:46:57

The strangest thing happened yesterday. My server stopped responding around lunch so after work I went home to see what was wrong but not ever responding physically. I killed the power and started moving it to my new apartment (thought I'd take the shoot since it was offline anyway).

Now to the problem: I've lost data since 6 Jul this year. The log (everything.log) says nothing special but the dates says: Jul 6 ... Oct 13. That's a few months there. The data is like it was back in July 6th so the files aren't removed from disk but changes after that date is not saved.

The setup
Running this machine with data loss as a VPS using qemu-kvm. The host machine handles the VPS's disks using lvm. That's Host creates a new lvm-volume which the guest OS uses. Both host and guest runs Arch Linux.

My first thought is that for some reason the data on the guest hasn't been saved to disk (although it seemed that way when using the guest machine) but rather just stacked in memory and not written to the guest's lvm-volume. I can't confirm this but there are a few things pointing towards this reasoning. 1. The server has 2GB RAM in total. The amount of data lost on the guest is about 1GB. If for some reason the lvm-volume saved the data in memory instead of writing to disk it makes a bit sense why the server just stopped working (when the RAM got full).

The guest runs ext4 btw and checking the host-log it says the same as the guest, last log was from Jul 6..

So what might have happened? I've settled with the data being lost and all (not that important, more of an irritation thing losing it) but I don't want this to happen again. Might it be what I'm guessing about lvm not writing to the lvm-volume-image and instead saving to ram or what's your opinion on this issue?

pyther · 2010-10-14 13:18:11

When was the last time your rebooted the server? I know there was some issues with ext4 and hard crashes when ext4 was rolled out in the kernel.

xintron · 2010-10-14 13:44:49

The kernel running is 2.6.33 (on both host and guest). So it might be a hard crash causing this problem? If so I will update the host right away later today

Arch Linux

#1 2010-10-14 06:46:57

Data loss

#2 2010-10-14 13:18:11

Re: Data loss

#3 2010-10-14 13:44:49

Re: Data loss

Board footer