search for: nodatacow

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 tre...

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 ref...

To reproduce the bug: # mount -o nodatacow /dev/sda7 /mnt/ # dd if=/dev/zero of=/mnt/tmp bs=4K count=1 1+0 records in 1+0 records out 4096 bytes (4.1 kB) copied, 0.000136115 s, 30.1 MB/s # dd if=/dev/zero of=/mnt/tmp bs=4K count=1 conv=notrunc oflag=direct dd: writing `/mnt/tmp'': Input/output error 1+0 records in 0+...

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 tho...

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 COW, one with nodatacow Any ideas why the flags are being ignored? I''m running 32bit 3.3rc4 with noatime,nodatasum,space_cache,autodefrag,inode_cache o...

...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 /dev/sdX Finally I have some small concern about two macro (see below) >----Messaggio originale---- >Da: seto.hidetoshi@jp.fujitsu.com >Data: 18/09/2012 3.30 >A: <linux-btrfs@vger.kernel.org> >Ogg: [PATCH 2/...

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

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, This patch simplifies the nodatacow checker. If all references were created after the latest snapshot, then we can avoid COW safely. This patch also updates run_delalloc_nocow to do more fine-grained checking. Regards Signed-off-by: Yan Zheng <zheng.yan@oracle.com> --- diff -urp 3/fs/btrfs/ctree.h 4/fs/btrfs/ctree.h --- 3/fs...

...ort * Subvolume quotas and inherited space usage information * Snapshot removal * QA Suite for automated regression testing * Reserved space for online fsck and the ability to add storage so that a * background extent allocation check can proceed * Additional ioctls to set per-inode attributes (nodatacow, nodatasum, etc) So I think all of those are still true. Things that I know are being worked on are * async block group cacheing - me * locking changes - Chris * backref stuff - Yan Som other things off the top of my head are * a better way to cache block groups in general, for this I was thin...

Hi, I am using 2.6.36.3 kernel with btrfs, 512MB memory and a very slow disk, no special options for mounting btrfs except noatime. Now I found it very slow. When I rm a 5GB movie, it took 20 secs. -- 竹密岂妨流水过 山高哪阻野云飞 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at

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 "unsubsc...

...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 into this cryptic warning on the chattr man page: (Note: For btrfs, the ''C'' flag should be set on new or empty files. If it is set on a file which already has data blocks, it is undefined when the blocks assigned to the file will be fully stable. I...

...r not. > - if you use barrier - both in the host and the guest. I noticed that when btrfs is mounted with default options, when writing i.e. 10 GB on the KVM guest using qcow2 image, 20 GB are written on the host (as measured with "iostat -m -p"). With ext4 (or btrfs mounted with nodatacow), 10 GB write on a guest produces 10 GB write on the host. -- Tomasz Chmielewski http://wpkg.org -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-in...

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

...details and example usage of the conversion program can be found here: http://oss.oracle.com/projects/btrfs/dist/documentation/btrfs-converter.html Thanks to Yan Zheng for all of his work on the converter. [ New mount options ] mount -o nodatacsum disables checksumming on data extents mount -o nodatacow disables copy on write of data extents, unless a given extent is referenced by more than one snapshot. This is targeted at database workloads, where copy on write is not optimal for performance. However the explicit back references allow the nodatacow code to make sure copy on write is done when...

...details and example usage of the conversion program can be found here: http://oss.oracle.com/projects/btrfs/dist/documentation/btrfs-converter.html Thanks to Yan Zheng for all of his work on the converter. [ New mount options ] mount -o nodatacsum disables checksumming on data extents mount -o nodatacow disables copy on write of data extents, unless a given extent is referenced by more than one snapshot. This is targeted at database workloads, where copy on write is not optimal for performance. However the explicit back references allow the nodatacow code to make sure copy on write is done when...

Hi, this shown up today. I had to do a hard reboot as graceful hanged on sync(). ------------[ cut here ]------------ kernel BUG at fs/btrfs/delayed-inode.c:1466! invalid opcode: 0000 [#1] SMP CPU 10 Modules linked in: btrfs zlib_deflate lzo_compress ipmi_devintf autofs4 be2iscsi iscsi_boot_sysfs ib_iser rdma_cm ib_cm iw_cm ib_sa ib_mad ib_addr iscsi_tcp bnx2i cnic uio ipv6 cxgb3i libcxgbi

...37418240 --bsrange=512b-64k --scramble_buffers=1 --nrfiles=1 --overwrite=1 --ioengine=sync --filename=file-1 --name=job0 --name=job1 --name=job2 --name=job3 --name=job4 --name=job5 --name=job6 --name=job7 The files are preallocated with fallocate before the fio run. Mount options: noatime,nodatasum,nodatacow,nospace_cache Can somebody please advise on how to address this issue, and, if possible, how to solve it on kernel 3.6. Thanks, Alex. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at h...

...ndex.php/Gotchas: Files with a lot of random writes can become heavily fragmented (10000+ extents) causing trashing on HDDs and excessive multi-second spikes of CPU load on systems with an SSD or large amount a RAM. On servers and workstations this affects databases and virtual machine images. The nodatacow mount option may be of use here, with associated gotchas. On desktops this primarily affects application databases (including Firefox and Chromium profiles, GNOME Zeitgeist, Ubuntu Desktop Couch, Banshee, and Evolution''s datastore.) Workarounds include manually defragmenting your home dire...