32
votes
Accepted
What ext4 functionality does btrfs not support?
Disadvantages of btrfs compared to ext4:
btrfs doesn't support badblocks
This means that if you've run out of spare non-addressable sectors that the HDD firmware keeps to cover for a limited number ...
- 31.5k
30
votes
Accepted
btrfs: how to calculate btrfs compression space savings?
In Debian/Ubuntu:
apt install btrfs-compsize
compsize /mnt/btrfs-partition
In Fedora:
dnf install compsize
compsize /mnt/btrfs-partition
output is like this:
Processed 123574 files, 1399139 regular ...
- 416
24
votes
Accepted
nice and ionice: which one should come first?
If nice caused lots of I/O, you would want to do:
ionice -c 3 nice ...
so that the impact of the I/O would be minimized.
Conversely, if ionice performed lots of computation, you would want to do
...
- 10.2k
21
votes
How to get rid of the “scanning for btrfs file systems” at start-up?
On Ubuntu 18.04 you can uninstall btrfs-support with
apt purge btrfs-progs
But that probably wouldn't save you much boot time. On my system the reason was, that I don't have a swap partition but on ...
- 29.6k
18
votes
What is the point of btrfs subvolumes?
I’m no expert—not even close!—but since I’ve been reading a lot about Btrfs lately, and since your question has gone unanswered for six months, I figured I’d give it a shot.
Here are two possible use ...
- 293
17
votes
How do I determine the block size for ext4 and btrfs filesystems?
You could use stat -f to get an answer of any filesystem, eg.:
% stat -f /home
File: "/home"
ID: 5013a37be3cd6a47 Namelen: 255 Type: ext2/ext3
Block size: 4096 Fundamental ...
- 3,176
16
votes
What ext4 functionality does btrfs not support?
As pointed out in the comments there is support for swap files as of kernel 5.0. albeit with some limitations, as listed at https://btrfs.readthedocs.io/en/latest/btrfs-man5.html:
SWAPFILE SUPPORT
A ...
- 5,983
15
votes
btrfs replace "ERROR: target device smaller than source device"
I encountered this when trying to replace a disk with one slightly smaller. I was getting this error even after resizing the filesystem on the source drive. Since I was using whole disks, there was no ...
- 702
15
votes
Accepted
Error for `mount`: `system call failed: File exists.`
(I'm not sure why you're using the -o loop mount option, as the LVM snapshot device should be just as good a disk device as its original is.)
"File exists" is the standard English text for errno ...
- 103k
15
votes
Accepted
How do I determine the block size for ext4 and btrfs filesystems?
You'll want to look at the data block allocation size, which is the minimum block that any file can allocate. Large files consist of multiple blocks. And there's always some "waste" at the ...
- 22.1k
13
votes
Accepted
Why is cp --reflink=auto not the default behaviour?
As of coreutils 9.0 reflink=auto is the default behaviour.
See:
https://lists.gnu.org/archive/html/info-gnu/2021-09/msg00010.html
This is to announce coreutils-9.0, a stable release.
This is a new ...
- 662
13
votes
Resize a btrfs partition inside a logical LVM volume
BTRFS takes filesystem mount point as an argument, not a device path.
In other words, intead of this:
btrfs filesystem resize max /dev/vg/lvhome
You should use actual path where the said volume was ...
- 1,436
13
votes
Accepted
How do I expand btrfs metadata?
TL;DR The metadata (if the btrfs is not suffering general low space condition) will automatically increase. In cases that no unallocated free space exists, the automatic increase is hembered. If, ...
- 14.7k
13
votes
Accepted
Can btrfs track / avoid bad blocks?
Sadly, no.
btrfs doesn't track bad blocks and btrfs scrub doesn't prevent the next file from hitting the same bad block(s).
This btrfs mailing list post suggests to use ext4 with mkfs.ext4 -c (this &...
- 31.5k
13
votes
Accepted
How to set a non default zstd compression level at btrfs filesystem defragment?
Kernel 5.1 added ZSTD level support. I tested it with rc1 today using a mount option compress=zstd:12 in /etc/fstab. The default level is 3. To be clear: The change affects only files that are written ...
- 275
13
votes
Accepted
How to encrypt an existing disk on Fedora without formatting?
This assumes a default Fedora installation, with the following Btrfs-based partitions:
Root partition (Btrfs subvolumes "root" [mounted at /] and "home" [mounted at /home])
Boot ...
- 195
12
votes
BTRFS convert RAID0 to RAID1
When making a btrfs filesystem across multiple devices, the default is to use RAID0 for data, and RAID1 for metadata. If you want to change this you can pass arguments to the mkfs command to change ...
- 804
12
votes
Accepted
Why would I want to disable Copy-On-Write while creating QEMU Images?
The performance degradation with VM images on BTRFS is not merely due to a lot of file writes; as far as BTRFS is concerned the writes are to the same file. The issue arises from a lot of random ...
- 7,278
12
votes
Get size of btrfs directory which may contain subvolumes
Yes, it's probably a BTRFS related issue.
As a general rule, classic du is not reliable with BTRFS, and quite often can give seemingly nonsensical results like this. This ultimately arises from the ...
- 12.3k
12
votes
Accepted
Serious backup options for linux disk (dmcrypt, luks, ext4, ext3, btrfs) normal and encrypted system
Linux system backup
When targeting a true full system backup, disk image backup (as asked) offer substantial advantage (detailed bellow) compared to files based backup.
With files based backup disk/...
- 14.7k
11
votes
Accepted
I have a disk failing in a RAID1 btrfs such that writes are iffy, but reads mostly work. How to replace it?
This has turned out to be a royal PITA. First, it's important to note that btrfs now has a proper replace command, which is very much better than add new, remove failing.
First, start by partitioning ...
- 111k
11
votes
Accepted
Btrfs RAID1: How to replace a disk drive that is physically no more there?
Update: According to @mkudlacek, this problem has been fixed.
For prosperity, here is my answer to why in 2017, I could not rebuild a RAID with a missing drive.
Turns out that this is a limitation of ...
- 523
11
votes
Btrfs RAID1: How to replace a disk drive that is physically no more there?
replace needs the filesystem to be mounted rw to operate.
In a degraded BTRFS RAID1 filesytem, you have one and only one chance to mount the filesystem rw using -o degraded:
degraded
(...
- 31.5k
11
votes
btrfs — Is it dangerous to defragment subvolume which has readonly snapshots?
Btrfs defrag won't break all reflinks
Just the particular instances you point it at. So, if you have subvolume A, and snapshots S1 and S2 of that subvolume A, then running defrag on just subvolume A ...
- 5,014
11
votes
Accepted
How to display btrfs snapshot size
Enabling quota is not a recommended if you have lot of backups.
Instead, you can use btrfs filesystem du -s command:
# btrfs filesystem du -s @snapshot*
Total Exclusive Set shared Filename
...
- 126
10
votes
Accepted
How do I view the btrfs checksum of a file?
Btrfs calculates a crc32c checksum for each file.
This is not correct. Both of the open-source checksumming file-systems (ZFS and BTRFS) calculate a checksum for each logical block (the unnamed ...
- 374
10
votes
Accepted
BTRFS balance completed, but still shows data stored in "single" mode
With the help of a user on the btrfs irc, I was able to answer question (1). It seems unrelated to the reboot and unsuccessful mount attempt (still not sure what that was about). Instead, it seems the ...
- 313
10
votes
Accepted
ENOSPC: Why is `btrfs balance` required? What does it do?
Unlike most conventional filesystems, BTRFS uses a two-stage allocator. The first stage allocates large regions of space known as chunks for specific types of data, then the second stage allocates ...
- 12.3k
10
votes
Accepted
What does a rmlint's "clone" for btrfs do?
The differences are somewhat subtle.
Reflink deletes the duplicate file and creates a new file in its place which is a clone of the original file. The metadata of the duplicate is lost, although ...
- 1,521
10
votes
Can I use btrfs subvolumes for trying multiple Linux distributions without committing a set quantity of disk space?
I have get it works, partially.
From an OpenSUSE installation (btrfs used by default), I have:
created a subvolume (btrfs subvol create /debian),
installed debootstrap,
deboostrap --arch=amd64 stable ...
- 2,808
Only top scored, non community-wiki answers of a minimum length are eligible