On 2018-01-22 21:35, Chris Murphy wrote:
On Mon, Jan 22, 2018 at 2:06 PM, Claes Fransson
<claes.v.frans...@gmail.com> wrote:
Hi!
I really like the features of BTRFS, especially deduplication,
snapshotting and checksumming. However, when using it on my laptop the
last couple of years, it has became corrupted a lot of times.
Sometimes I have managed to fix the problems (at least so much that I
can continue to use the filesystem) with check --repair, but several
times I had to recreate the file system and reinstall the operating
system.
I am guessing the corruptions might be the results of unclean
shutdowns, mostly after system hangs, but also because of running out
of battery sometimes?
I think it's something else because I intentionally and
unintentionally do unclean shutdowns (I'm really impatient and I'm a
saboteur) on my laptop and I never get corruptions. In 18 months with
an HP Spectre which doesn't even have ECC memory, and has an NVMe
drive, *and* really remarkable for almost half this time I used the
discard mount option which pretty much instantly obliterates unused
roots, even when referenced in the super block as backup roots - and
yet still zero corruption. No complaints on mount, scrub, or readonly
checks. *shrug*
Anyway I suspect hardware or power issue. Or even SSD firmware issue.
I would tend to agree here, with one caveat, if it's a laptop that's
less than 3 years old, you can probably rule out power issues. Some
more info on the particular system might help identify what's wrong.
Furthermore, the power-led has recently started blinking (also when
the power-cable is plugged in), I guess because of an old and bad
battery. Maybe the current corruption also can have something to do
with this? However I almost always run with power cable plugged in in
last year, only on battery a few seconds a few times when moving the
laptop.
Currently, I can only mount the filesystem readonly, it goes readonly
automatically if I try to mount it normally.
Btrfs is confused and doesn't want to make the corruption worse. >
Fstab mount options: noatime,autodefrag (I have been using the option
nossd with older kernels one period in the past on the filesystem).
If it matters, I have been running duperemove many times on the
filesystem since creation.
I don't think it's related.
To test the RAM, I have been running mprime Blend-test for 24 hours
after the corruption without any error or warning.
I'm not familiar with it, pretty sure you want this for UEFI:
https://www.memtest86.com/download.htm
Where you can use that or memtest86+ if the firmware is BIOS based.
Do keep in mind that just because it passes memory checks does not mean
it's not an issue with the RAM. Memory testers rarely throw false
positives, but it's pretty common to get false negatives from them.>
I have never noticed any corruptions on the NTFS and Ext4 file systems
on the laptop, only on the Btrfs file systems.
NTFS and ext4 likely won't notice such corruptions either (although
new ext4 volumes any day now will have checksummed metadata by
default) as they're weren't designed with such detection in mind.
This is extremely important to understand. BTRFS and ZFS are
essentially the only filesystems available on Linux that actually
validate things enough to notice this reliably (ReFS on Windows probably
does, and I think whatever Apple is calling their new FS does too).
Even if ext4 did notice it, it would just mark the filesystem for a
check and then keep going without doing anything else about it
(seriously, the default behavior for internal errors on ext4 is to just
continue like nothing happened and mark the FS for fsck).
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