similar to: Fwd: [virt-devel] btrfs NOCOW for VM disk images

Add ''-C'' (nocow) option to vhd-util create. Btrfs has terrible performance when hosting VM images, even more when the guest in those VM are also using btrfs as file system. One way to mitigate this bad performance is to turn off COW attributes on VM files (since having copy on write for this kind of data is not useful). According to ''chattr'' manpage, NOCOW

What happens if you set an individual file inside a subvolume as nocow (chattr +C) and then take a snapshot of that subvolume and modify the file in both? Will btrfs now ignore the nocow attribute completely or will it do "as few copies as possible"? (I''d love to know if it''s possible to visualize the fragmentation of a single file.) -- To unsubscribe from this list:

Balance will create reloc_root for each fs root, and it''s going to record last_snapshot to filter shared blocks. The side effect of setting last_snapshot is to break nocow attributes of files. So it turns out that checking last_snapshot does not always ensure that a node/leaf/file_extent is shared. That''s why shared node/leaf needs to search extent tree for number of

I set the C (NOCOW) and z (Not_Compressed) flags on a folder but the extent counts of files contained there keep increasing. Said files are large and frequently modified but not changing in size. This does not happen when the filesystem is mounted with nodatacow. I''m using this as a workaround since subvolumes can''t be mounted with different options simultaneously. ie. one with

Hello, some time ago we discussed on #btrfs that the nocow attribute for files wasn''t working (around 3.3 or 3.4 kernels). That was evident by files fragmenting even with the attribute set. Chris mentioned to find a fix quickly for that, and posted some lines of change into irc. But recently someone mentioned that 3.6-rc looks like still not respecting nocow for files. Is there really

Hello, is it possible to set nodatacow on a per-file basis? I couldn''t find anything. If not, wouldn''t that be a great feature to get around the performance issues with VM and database storage? Of course cloning should still cause COW. Thanks, Ralf-Peter -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to

I want to eliminate the COW feature on all of my OS files. It is a nice feature for user files, but I don''t see a clear benefit for the actual OS files. And I suspect that COW induced fragmentation is causing or aggravating problems with my system including the boot open_ctree problem. I had planned to recursively chattr these files to "nodatacow" status but then I ran

Hi everyone, I described the reflink operation at the Linux Storage & Filesystems Workshop last month. Originally implemented as an ocfs2-specific ioctl, the consensus was that it should be a syscall from the get-go. Here's some first-cut patches. For people who have not seen reflink, either at LSF or on the ocfs2 wiki, the first patch contains Documentation/filesystems/reflink.txt to

Hi, After reading through the btrfs documentation I''m curious to know if it''s possible to ever securely erase a file from a btrfs filesystem (or ZFS for that matter). On non-COW filesystems atop regular HDDs one can simply overwrite the file with zeros or random data using dd or some other tool and rest assured that the blocks which contained the sensitive information have

Hello, I''d like to know if there has been any discussion about adding a new feature to write (add) data at an offset, but without overwriting existing data, or re-writing the existing data. Essentially, in-place addition/removal of data to a file at a place other than the end of the file. Some possible use-cases of such a feature would be: (a) Databases (currently hack around this by

I have a 3 disk raid1 filesystem mounted with nodatacow. I have a folder in said filesystem with the ''C'' NOCOW & ''Z'' Not_Compressed flags set for good measure. I then copy in a large file and proceed to make random modifications. Filefrag shows no additional extents created, good so far. A big thank you to the those devs who got that working. However, after

https://bugzilla.samba.org/show_bug.cgi?id=10170 Summary: rsync should support reflink similar to cp --reflink Product: rsync Version: 3.1.0 Platform: All OS/Version: All Status: NEW Severity: normal Priority: P5 Component: core AssignedTo: wayned at samba.org ReportedBy: samba at shubin.ca

I realise that the hard link limit is in the queue to fix, and I read the recent thread as well as the older (october I think) thread. I just wanted to note that BackupPC *does* in fact run into the hard link limit, and its due to the dpkg configuration scripts. BackupPC hard links files with the same content together by scanning new files and linking them together, whether or not they started

What are the recommendations for running KVM images on BTRFS systems using kernel 3.4?  I saw older posts on the web complaining about poor performance, but I know a lot of work has gone into btrfs since then.  There also seemed to be the nocow option, but I didn''t find anything that said it actualy helped. Anybody have ideas? Thanks, Matt -- To unsubscribe from this list: send the line

On Fri, May 01, 2020 at 09:27:58PM +0200, A L via samba wrote: > > Jeremy. > I did not use a command line, but rather File Explorer > 1) In File explorer, go to \\SAMBA\share_io_uring\ > 2) Select folder "test2-ro" and choose copy > 3) Paste to a local drive > > The amount of files not working seems to vary, but usually within the 10 > first copied files. You

Glück Auf! I know its been discussed more then ones, but as a user I really would like to see the patch for allowing this in the kernel. Some users tested this patch successfully for weeks or months in 2 or 3 kernel versions since then, true? I''d say by creating a snapshot, it''s nothing else in the end. More then one file or tree sharing the same data on disc, or am I wrong?

Hi all, Just a quick question but can''t find an obvious answer. Can I create/convert a existing (btrfs) directory into a subvolume? It would be very helpful when transferring ''partitions'' into btrfs. I found a similar question way back in google, but that site is down now generally. Thanks in advance. -- To unsubscribe from this list: send the line

Hi, I have a home server on Linux Arch (kernel 3.11.2) that uses multi-device btrfs on root filesystem. Until recently it worked completely fine. And yesterday I rebooted it and the machine did not wake up. I booted from a USB (kernel 3.10) and tried to mount the filesystem. Here is OOPs I see [ 41.676217] device fsid 25e6a6fa-fe1f-4be5-a638-eeac948f8c21 devid 8 transid 164237 /dev/sda [

The rule originally comes from nocow writing, but snapshot-aware defrag is a different case, the extent has been writen and we''re not going to change the extent but add a reference on the data. So we''re able to allow such compressed extents to be merged into one bigger extent if they''re pointing to the same data. Signed-off-by: Liu Bo <bo.li.liu@oracle.com> ---

Chris Adams linux at cmadams.net Wed Jun 24 19:06:19 UTC 2015 >Btrfs may eventually obsolete a lot of > uses of LVM, but that's down the road. LVM is the emacs of storage. It'll be here forever. Btrfs doesn't export (virtual) block devices like LVM can, so it can't be a backing for say iSCSI. And it's also at the moment rather catatonic when it comes to VM images. This