similar to: How do I safely terminate COW on pre-existing files?

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

----- 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

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:

Add the missing usage for No_COW since we''ve supported No_COW flag. Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com> --- misc/chattr.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/misc/chattr.c b/misc/chattr.c index 141ea6e..24254cc 100644 --- a/misc/chattr.c +++ b/misc/chattr.c @@ -83,7 +83,7 @@ static unsigned long sf; static void usage(void) {

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

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

Add the missing usage for No_COW since we''ve supported No_COW flag. Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com> --- v1->v2: sort options alphabetically, thanks to Roman Mamedov. misc/chattr.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/misc/chattr.c b/misc/chattr.c index 141ea6e..24254cc 100644 --- a/misc/chattr.c +++ b/misc/chattr.c @@ -83,7

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

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

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 [

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

Hi, If i set strict allocate = yes in samba to speed up the transfer of a mssql database dump, then btrfs does not compress the file. I have tried it also by just copying a small file in Windows to the samba share and the same. I have tried btrfs mount options autodefrag and then btrfs fi defrag -c and the file still does not get compressed. I have tried kernels 3.6.11, 3.8 and 3.10.7 on FC16

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

Hello, This patch fixes the nodatacow check. The new test function can always detect extents referenced by multiple snatshots. If a extent was allocated in recent two transactions and no snapshot happened in these two transactions, we can always avoid cow. To check given extent''s reference, the test function walks down old tree root, then check backref info in the path. This initial

Hello, This is updated version of nodatacow patch. To check whether a given file extent is referenced by multiple snapshots, the checker walks down the fs tree through dead root and checks all tree blocks in the path. We can easily detect whether a given tree block is directly referenced by other snapshot. We can also detect any indirect reference from other snapshot by checking

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

I just pushed some code into the compiz repository for initial metacity theme support. It's not complete, left and right borders are not rendered correctly, button decorations doesn't always match event window locations, maximized and shaded windows are not rendered as when running metacity, button locations are not configurable as with metacity... but it still seem to look OK with most

Christoph Hellwig wrote: > There are a lot of variables when using qemu. > > The most important one are: > > - the cache mode on the device. The default is cache=writethrough, > which is not quite optimal. You generally do want to use cache=none > which uses O_DIRECT in qemu. > - if the backing image is sparse or not. > - if you use barrier - both in the host

SAMSUNG SSD 830 Series CPU0: Intel® Core(TM) i7-2820QM CPU @ 2.30GHz (fam: 06, model: 2a, stepping: 07) 8GB RAM (quite heavily tested, not recently, with several days of memtest) kernel 3.11.1-200.fc19.x86_64 running on baremetal btrfs-progs-0.20.rc1.20130308git704a08c-1.fc19.x86_64 Today I did a scrub on a btrfs volume, with no message or errors in console or dmesg or journal. Immediately after