Questions tagged [copy-on-write]
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23 questions
2 votes
0 answers
683 views
Btrfs : compress and nodatacow priority + automation
I have a btrfs partition mounted on / with compression enabled: mount -o subvol=@,defaults,noatime,nodiratime,compress=zstd,space_cache=v2 /dev/mapper/archlinux /mnt I want to disable the CoW ...
- 235
3 votes
1 answer
1k views
Copy on write for directories?
Some file-systems notably XFS and btrfs support Copy on Write at block level for files. This is done by reflinking where the underlying blocks are shared between files until they are modified. Since a ...
- 692
1 vote
0 answers
50 views
Is the stack of a forked process shared with its parent? [duplicate]
Is the stack of a forked process shared with its parent? If so, does this happen via shared copy-on-write pages?
- 1,704
6 votes
1 answer
4k views
In what ways is the COW filesystem an improvement over the Journaling Filesystem?
I don't think an informative answer exists on u&l or otherwise, which mentions why COW filesystems are a leg-up over any of the three modes of journaling. How does the former provide both superior ...
- 878
5 votes
4 answers
5k views
How to check disk usage for folders containing reflinked files on XFS?
XFS supports copy on write (CoW), so it is not entirely clear what du will say if some of the bytes are shared across files. I'd like to find a way to check how much disk space a folder uses, not ...
- 449
-2 votes
1 answer
103 views
snapshot management tool implementation
I want to implement a command-line tool that allows me to take snapshots of the filesystem for linux/unix systems. I know there are various ways to implement snapshot Copy-On-Write Redirect-On-Write ...
- 1
1 vote
1 answer
1k views
How to disable BTRFS copy-on-write updates for a subvolume using btrfs-property instead of chattr
I want to disable BTRFS copy-on-write updates for a subvolume using the newer method btrfs property instead of the old method chattr. I found the man page here: Manpage/btrfs-property - btrfs Wiki ...
- 19k
4 votes
0 answers
3k views
Recovering an overwritten file on ZFS
Is there any way to recover a deleted or overwritten file on ZFS? I accidentally overwrote a JPG file with a scanned image. Unfortunately, I didn’t take a snapshot beforehand. However, since ZFS uses ...
- 41
10 votes
2 answers
7k views
How does ZFS copy on write work for large files
Let's say I have a large file (8GB) called example.log on ZFS. I do cp example.log example.bak to make a copy. Then I add or modify a few bytes in original file. What will happen? Will ZFS copy the ...
- 203
1 vote
1 answer
507 views
A good way how to backup user data in CentOS?
I need to back up my data and I have not found a good way so far. Just say I have 1 TB of a non-system disk with 50-100 GB of user data (binary files, source code, images, etc.). And another big disk,...
- 39
0 votes
2 answers
6k views
Is copy-on-write not implemented based on page fault?
Operating System Concepts say fork() we can use a technique known as copy-on-write, which works by allowing the parent and child processes initially to share the same pages. ... When it is ...
- 107k
1 vote
1 answer
2k views
fork() and COW behavior after exec()
We understand the COW behavior after a fork (as for example described here) as follows: fork creates a copy of the parent's page table for the child and marks the physical pages read only, so if any ...
- 113
0 votes
1 answer
741 views
can two running processes share the complete process image in physical memory, not just part of it?
can two running processes share the complete process image in physical memory, not just part of it? Here I am talking about the Linux operating systems(eg. Ubuntu). My thinking: I think it is ...
- 101
0 votes
1 answer
142 views
Report directories with contents that exist elsewhere even if scattered
I want to generate a report of directories that I know I can safely delete (even if requiring a quick manual verification), because I know that the full contents all the way down, exist elsewhere--...
- 469
1 vote
1 answer
835 views
Doesn't the existence of LVM snapshots slows down writing a file system wich doesn't support them natively?
As far as understand snapshots in LVM (please, do correct me if I'm wrong): since they are not persistent and work even with a file system which doesn't itself support snapshots => I suppose it must ...
- 324