similar to: Set nodatacow per file?

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

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 If I want to manage a complete disk with btrfs, what''s the "Best Practice"? Would it be best to create the btrfs filesystem on "/dev/sdb", or would it be better to create just one partition from start to end and then do "mkfs.btrfs /dev/sdb1"? Would the same recomendation hold true, if we''re talking about huge disks, like 4TB or so?

I've just tried putting usr in a subvol. Installation proceeds normally, no errors, but I'm dropped to a dracut prompt which indicates mount of /usr failed. dmesg follows: [ 14.025215] systemd[1]: Starting dracut initqueue hook... [ 14.077890] Btrfs loaded [ 14.129987] device label fedora_f18v devid 1 transid 31 /dev/sda1 [ 14.313607] device label fedora_f18v devid 1 transid 31

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

----- Forwarded Message ----- From: "Stefan Hajnoczi" <stefanha@redhat.com> To: "Eric Sandeen" <sandeen@redhat.com> Cc: virt-devel@redhat.com, "Kevin Wolf" <kwolf@redhat.com> Sent: Friday, November 22, 2013 9:20:51 AM Subject: [virt-devel] btrfs NOCOW for VM disk images Hi, In upstream QEMU we''re discussing patches that set the NOCOW flag

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

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

In btrfs if we mount with "compress" we have no way to disable compressing by remounting (mount -o remount /mnt/btrfs), only by unmounting and mounting without "compress". This patch adds "nocompress" mount option which can be used to remount the filesystem without compression: # mount -o remount,nocompress /mnt/btrfs This option is usefull in cases when we have a

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

Hi Seto, please could you update also the man page too ? Why it was not provided a way to clear a *single* flag ? To me it seems a bit too long to clear all the flag (btrfs mount-option clear) and then set the right one. As user interface I suggest something like chmod: btrfs mount-option set +ssd,skip_balance -nodatacow /dev/sdX or btrfs mount-option set =ssd,skip_balance,nodatacow

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:

Glück Auf! I use now kernel 3.2. The filesystem was originally created under 2.6.39 on 1 whole hdd, mounted with "noatime,nodiratime,inode_cache". I use it for backups: rsync the whole system to a subvolume, snapshot it and then delete some tempfiles in the snapshot, which are 90% of the full-backup, all once a day. In figures: on this 1 TB hdd is the full-backup with around 600 GiB and

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> ---

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''m currently trying to understand how compression in btrfs works. I could not find any detailed description about it. So here are my questions. 1. How is decided what to compress and what not? After a fast test with a 2g image file, I''ve looked into the extents of that file with find-new and it turned out that only some of the first extents were compressed. The file was

Hello, On a newly created filesystem with btrfs-progs-git-20111009 and the 3.1.0-rc8 kernel I am getting the following error when doing btrfsck after main OS installation fs tree 256 refs 2 unresolved ref root 256 dir 256 index 2 namelen 8 name __active error 600 found 4215058432 bytes used err is 1 total csum bytes: 3962760 total tree bytes: 157192192 total fs tree bytes: 146976768

Hello, Trying to balance a 2TB filesystem on the 3.8.5 kernel: Label: ''p2'' uuid: 01f6cc8b-d305-40e1-bac8-8fdd548f611e Total devices 1 FS bytes used 1.32TB devid 1 size 1.80TB used 1.37TB path /dev/sda2 System: total=4.00MB, used=156.00KB Data+Metadata: total=1.37TB, used=1.32TB I am getting a Segmentation fault in ''btrfs'' utility, and following in

As I''ve been using btrfs with an external USB drive, I wonder how to handle efficiently the compression setting. When I plug a drive in to ubuntu, it is automatically mounted. Its mounted without the compression option as its not in fstab. I don''t see it as desirable to install each usb drive in fstab on each computer that it may be used just so that compression is

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 [