Messages in this thread |  | | Date | Mon, 3 Sep 2001 00:28:18 +0300 | From | VDA <> | Subject | COW fs (Re: Editing-in-place of a large file) |
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Sunday, September 02, 2001, 11:21:37 PM, Bob McElrath wrote: BM> I would like to take an extremely large file (multi-gigabyte) and edit BM> it by removing a chunk out of the middle. This is easy enough by BM> reading in the entire file and spitting it back out again, but it's BM> hardly efficent to read in an 8GB file just to remove a 100MB segment.
BM> Is there another way to do this?
BM> Is it possible to modify the inode structure of the underlying BM> filesystem to free blocks in the middle? (What to do with the half-full BM> blocks that are left?) Has anyone written a tool to do something like BM> this?
BM> Is there a way to do this in a filesystem-independent manner?
A COW fs is a far more useful and cool. A fs where a copy of a file does not duplicate all blocks. Blocks get copied-on-write only when copy of a file is written to. There could be even a fs compressor which looks for and merges blocks with exactly same contents from different files.
Maybe ext2/3 folks will play with this idea after ext3?
I'm planning to write a test program which will scan my ext2 fs and report how many duplicate blocks with the same contents it sees (i.e how many would I save with a COW fs) -- Best regards, VDA mailto:VDA@port.imtp.ilyichevsk.odessa.ua http://port.imtp.ilyichevsk.odessa.ua/vda/
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