similar to: Impossible or Possible to Securely Erase File on Btrfs?

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

I''m looking to try BTRFS on a SSD, and I would like to know what SSD optimizations it applies. Is there a comprehensive list of what ssd mount option does? How are the blocks and metadata arranged? Are there options available comparable to ext2/ext3 to help reduce wear and improve performance? Specifically, on ext2 (journal means more writes, so I don''t use ext3 on SSDs,

I''ve got two recent examples of SSDs. Their pristine state from the manufacturer shows: Device Model: OCZ-VERTEX3 # hexdump -C /dev/sdd 00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 1bf2976000 Device Model: OCZ VERTEX PLUS (OCZ VERTEX 2E) # hexdump -C /dev/sdd 00000000 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................| *

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

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

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

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:

Hi! With 3.2-rc4 (probably earlier), Ext4 seems to remember what areas it trimmed: merkaba:~> fstrim -v /boot /boot: 224657408 bytes were trimmed merkaba:~> fstrim -v /boot /boot: 0 bytes were trimmed But BTRFS does not: merkaba:~> fstrim -v / /: 4431613952 bytes were trimmed merkaba:~> fstrim -v / /: 4341846016 bytes were trimmed Is it planned to add this feature to BTRFS

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

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

The Wiki does not make it clear as to why adding a secondary device defaults to RAID1 metadata and RAID0 data. I bought two SSDs with the intention of doing a BTRFS RAID0 for my root. What is the difference between forcing RAID0 on metadata and data as opposed to the default behavior? Can anyone clarify that? Thank you for your time, Mario -- To unsubscribe from this list: send the line

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

For using SSDs: Are there any format/mount parameters that should be set for using btrfs on SSDs (other than the "ssd" mount option)? General questions: How long is the ''delay'' for the delayed alloc? Are file allocations aligned to 4kiB boundaries, or larger? What byte value is used to pad unused space? (Aside: For some, the erased state reads all 0x00, and for

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, 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 [

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

Does BTRFS perform any journal and/or filesystem structure alignment (for benefit to SSD longevity and SSD, RAID array and large-sector device performance) at present? ext4''s Ted Tso will deliver 128KB alignment with the next release of e2fsprogs (ie 1.41.4) [1], so perhaps it''s a good idea for btrfsprogs also, if not already available? Daniel --- [1]

Is this useful to anyone? Got this after a crash/reboot: if (block_rsv) { WARN_ON(block_rsv->size > 0); <<<<<<<<<<<<<<<<<<<<<< btrfs_free_block_rsv(root, block_rsv); } ------------[ cut here ]------------ WARNING: at fs/btrfs/inode.c:2165 btrfs_orphan_commit_root+0xcb/0xdf() Hardware name: 2429A78 Modules linked in:

Hello list, i know what btrfs don''t support swap files. I read arch wiki and when i reading about systemd addon for auto create swapfile on btrfs, i invent the way, how create and using swap file, just see following sh code: swapfile=$(losetup -f) #free loop device truncate -s 8G /swap #create 8G sparse swap file losetup $swapfile /swap #mount file to loop mkswap $swapfile swapon