Re: [Fwd: Re: Linking two files together][RFC]
On Wed, 9 Jun 2010, Roberto Ragusa wrote: > I hope that ideas about btrfs are not off-topic for this mailing list. > > The forwarded message below was written by me on fedora-users. > The thread is about the ability to link two files in a manner > similar to "cat 1 2 >3 && rm 1 2" while avoiding any data > movement on the disk. > The implementation should just put the original extents together in > the new file. Is there any filesystem which is capable of doing that? > As btrfs is already based on extents and COW, couldn't this feature be > evaluated for feasibility? I think a lot of usages will be found > for it if actually implemented. Btrfs already has a CLONE_RANGE ioctl that will clone a range of (block-aligned) bytes from file A to any offset in file B. The fs just fixes up the file metadata to reference the same bytes on disk without reading or writing any actual file data. sage -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [Fwd: Re: Linking two files together][RFC]
Roberto Ragusa writes: > I hope that ideas about btrfs are not off-topic for this mailing list. > > The forwarded message below was written by me on fedora-users. > The thread is about the ability to link two files in a manner > similar to "cat 1 2 >3 && rm 1 2" while avoiding any data > movement on the disk. OCFS2 can do this today with "reflinks" -Andi -- a...@linux.intel.com -- Speaking for myself only. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [Fwd: Re: Linking two files together][RFC]
On Wednesday 09 June 2010 13:53:00 Roberto Ragusa wrote: > Hi, > > I hope that ideas about btrfs are not off-topic for this mailing list. > > The forwarded message below was written by me on fedora-users. > The thread is about the ability to link two files in a manner > similar to "cat 1 2 >3 && rm 1 2" while avoiding any data > movement on the disk. > The implementation should just put the original extents together in > the new file. Is there any filesystem which is capable of doing that? > As btrfs is already based on extents and COW, couldn't this feature be > evaluated for feasibility? I think a lot of usages will be found > for it if actually implemented. It will come naturally with online data deduplication -- though, at the moment the only FS I know of that can do this is ZFS. Otherwise, we would need a completely new system calls to perform those operations. > > Read the following part if interested. > > Thanks. > > Original Message > From: - Thu May 27 20:44:26 2010 > X-Mozilla-Status: 0001 > X-Mozilla-Status2: > Message-ID: <4bfe537b.8050...@robertoragusa.it> > Date: Thu, 27 May 2010 13:11:55 +0200 > From: Roberto Ragusa > User-Agent: Thunderbird 2.0.0.23 (X11/20090825) > MIME-Version: 1.0 > To: Community support for Fedora users > Subject: Re: Linking two files together > References: > <7f593570d3366e4e85c76baf70fd0eed0106dbf31...@cvmmbx.vetmed.wsu.edu> > <4bfd589f.7090...@kjchome.homeip.net> In-Reply-To: > <4bfd589f.7090...@kjchome.homeip.net> > X-Enigmail-Version: 0.96.0 > Content-Type: text/plain; charset=ISO-8859-1 > Content-Transfer-Encoding: 7bit > > Kevin J. Cummings wrote: > > On 05/26/2010 01:16 PM, Rector, David wrote: > >> Hello, > >> > >> I have studied various filesystems, and am fairly familiar with how they > >> are structured. However, I am currently stuck on trying to do what > >> seems like a simple thing. > >> > >> I would like to join two files together without having to physically > >> copy bytes (i.e. I have vary large files, so I don't want to use > >> 'cat'). It seems to me that it should be possible to simply modify the > >> file entry in the filesystem such that the last inode of the first file > >> points to the first inode of the second file. I guess this is similar > >> to a "hard link", but used to join files rather than simply have > >> another pointer to one file. > >> > >> I have seen 'mmv' and 'lxsplit' and they all seem to do the same thing, > >> namely they want to physically copy the bytes in order to join two > >> files together. > >> > >> Is there any such utility in linux to perform such a hard link to join > >> or connect two files together without having to copy bytes? > > > > If you could guarantee that the last extent used by the first file was > > completely full of data with no extraneous bytes, it might be possible > > to "merge" the extent maps of the 2 files into a single file entry. If > > you cannot guarantee that, then you will have to copy bytes from the 2nd > > file to the end of the first file. > > But everything becomes possible if the fileystem permits partially empty > blocks in the middle of the file. No filesystem does it AFAIK, but it is > not a big issue, as partial blocks (or compacted tails) are already > permitted at the end of the file. New filesystems use extents rather than > blocks, so if the extents are measured in bytes instead of 512b-blocks you > can just use a smaller extent in the middle of the file where the join > happened. > > At this point, you can support inplace-joining, inplace-inflating (add > 1 bytes in this file at position 30), inplace-erasure (remove > 1 bytes at position 30) and data shuffling (swap the first 50meg > of the file with the last 50meg). > > With heavy usage you have just created a new kind of fragmentation, which > can be corrected with the usual defragmentation tools (including "cp"). > (add that fragmentation is losing importance with the spreading of SSD) > > Considering that sparse files have been a reality for decades and that > the implementation of operation with inside-file byte-grained extents > is not more difficult than truncate, I wonder if we will see something > of this kind in some advanced filesystem (btrfs?). > > There are a lot of possible uses: > - delete/replace mail in mbox format repositories > - smart packaging (delete from tar, delete from zip) > - in-place iso creation > and just imagine. > - video editing (!) add/remove/replace frames inside a 150GiB captured > video > > Where can you submit ideas to btrfs? > It also has COW, so everything becomes even more exciting... -- Hubert Kario QBS - Quality Business Software 02-656 Warszawa, ul. Ksawerów 30/85 tel. +48 (22) 646-61-51, 646-74-24 www.qbs.com.pl System Zarządzania Jakością zgodny z normą ISO 9001:2000 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More major
[Fwd: Re: Linking two files together][RFC]
Hi, I hope that ideas about btrfs are not off-topic for this mailing list. The forwarded message below was written by me on fedora-users. The thread is about the ability to link two files in a manner similar to "cat 1 2 >3 && rm 1 2" while avoiding any data movement on the disk. The implementation should just put the original extents together in the new file. Is there any filesystem which is capable of doing that? As btrfs is already based on extents and COW, couldn't this feature be evaluated for feasibility? I think a lot of usages will be found for it if actually implemented. Read the following part if interested. Thanks. Original Message From: - Thu May 27 20:44:26 2010 X-Mozilla-Status: 0001 X-Mozilla-Status2: Message-ID: <4bfe537b.8050...@robertoragusa.it> Date: Thu, 27 May 2010 13:11:55 +0200 From: Roberto Ragusa User-Agent: Thunderbird 2.0.0.23 (X11/20090825) MIME-Version: 1.0 To: Community support for Fedora users Subject: Re: Linking two files together References: <7f593570d3366e4e85c76baf70fd0eed0106dbf31...@cvmmbx.vetmed.wsu.edu> <4bfd589f.7090...@kjchome.homeip.net> In-Reply-To: <4bfd589f.7090...@kjchome.homeip.net> X-Enigmail-Version: 0.96.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Kevin J. Cummings wrote: > On 05/26/2010 01:16 PM, Rector, David wrote: >> Hello, >> >> I have studied various filesystems, and am fairly familiar with how they are >> structured. However, I am currently stuck on trying to do what seems like a >> simple thing. >> >> I would like to join two files together without having to physically copy >> bytes (i.e. I have vary large files, so I don't want to use 'cat'). It seems >> to me that it should be possible to simply modify the file entry in the >> filesystem such that the last inode of the first file points to the first >> inode of the second file. I guess this is similar to a "hard link", but used >> to join files rather than simply have another pointer to one file. >> >> I have seen 'mmv' and 'lxsplit' and they all seem to do the same thing, >> namely they want to physically copy the bytes in order to join two files >> together. >> >> Is there any such utility in linux to perform such a hard link to join or >> connect two files together without having to copy bytes? > > If you could guarantee that the last extent used by the first file was > completely full of data with no extraneous bytes, it might be possible > to "merge" the extent maps of the 2 files into a single file entry. If > you cannot guarantee that, then you will have to copy bytes from the 2nd > file to the end of the first file. But everything becomes possible if the fileystem permits partially empty blocks in the middle of the file. No filesystem does it AFAIK, but it is not a big issue, as partial blocks (or compacted tails) are already permitted at the end of the file. New filesystems use extents rather than blocks, so if the extents are measured in bytes instead of 512b-blocks you can just use a smaller extent in the middle of the file where the join happened. At this point, you can support inplace-joining, inplace-inflating (add 1 bytes in this file at position 30), inplace-erasure (remove 1 bytes at position 30) and data shuffling (swap the first 50meg of the file with the last 50meg). With heavy usage you have just created a new kind of fragmentation, which can be corrected with the usual defragmentation tools (including "cp"). (add that fragmentation is losing importance with the spreading of SSD) Considering that sparse files have been a reality for decades and that the implementation of operation with inside-file byte-grained extents is not more difficult than truncate, I wonder if we will see something of this kind in some advanced filesystem (btrfs?). There are a lot of possible uses: - delete/replace mail in mbox format repositories - smart packaging (delete from tar, delete from zip) - in-place iso creation and just imagine. - video editing (!) add/remove/replace frames inside a 150GiB captured video Where can you submit ideas to btrfs? It also has COW, so everything becomes even more exciting... -- Roberto Ragusamail at robertoragusa.it -- Roberto Ragusamail at robertoragusa.it -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
