LVM + snapshots force shutdown rescue?

Cube777 · 2016-05-08 11:29:58

Hi fellow Archers,

I am for one, extremely OCD about everything on my PC. This is partially why I love Arch so much (no bloat - juuust perfect . This also means that I struggle when a force shutdown or something similiar occurs... It pains me to see the
"orphaned inode" message on startup and I usually go paranoid about data loss. I would like to know if using a LVM setup with snapshotting of / while the PC is being run would solve this problem (this excludes my home folder + swap to reduce IO traffic)? So when a force shutdown occurs I just merge the snahpshot into my root LV? Or am I just complicating my life to no avail? Also - I saw some reports of LVM snapshotting severely degrading IO performance, but these reports were all relatively old. Is this still relevant? Can setting up a second HDD to hold the snapshot solve performance problems? Any replies would be greatly appreciated, thanks

Last edited by Cube777 (2016-05-08 11:46:11)

frostschutz · 2016-05-08 11:40:11

...if you merge an old snapshot, would that not lose you even more files than whatever the power loss caused you to lose?

Of course a snapshot will lose you performance, it makes a copy first for every write you make... so instead of (write) you have (read, write, write).

I wouldn't use snapshots this way. What you need are real backups. And a reliable power supply to avoid unnecessary mishaps...

Cube777 · 2016-05-08 12:02:53

The idea was that even though I might lose an update or two or some config changes I can restore to a complete and working system. Since most of my work is done in my home folder ideally not much should be lost from merging the snapshot. A situation that occured recently - I was using a systemd-nspawn container and I did something wrong and the end result was my system completely hanging. This lead to a long list of inodes being orphaned which maybe could've been avoided with snapshots. Snapshots seemed to be a good replacement for full system backups since were made on the fly.

But thanks - I'll do some more research on full system backups and so forth (tarring snapshots seems to be a good way to go).

frostschutz · 2016-05-08 12:08:37

Did you try Magic Sysrq + R E I S U B? That usually still works even if everything else is hanging. As long as the kernel didn't outright panic...

Cube777 · 2016-05-08 12:18:56

I have never before heard of that (Only been a linux user for about a year and a half now) - thank you very much, it woud've saved me a few times by now.

Arch Linux

#1 2016-05-08 11:29:58

LVM + snapshots force shutdown rescue?

#2 2016-05-08 11:40:11

Re: LVM + snapshots force shutdown rescue?

#3 2016-05-08 12:02:53

Re: LVM + snapshots force shutdown rescue?

#4 2016-05-08 12:08:37

Re: LVM + snapshots force shutdown rescue?

#5 2016-05-08 12:18:56

Re: LVM + snapshots force shutdown rescue?

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