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Re: Pity userspace on where this is done on a simple minded filesystem

Re: Pity userspace on where this is done on a simple minded filesystem

Posted May 6, 2009 0:12 UTC (Wed) by adj (subscriber, #7401)
In reply to: Re: Pity userspace on where this is done on a simple minded filesystem by daney
Parent article: The two sides of reflink()

Where does my filesystem get 200Gbyte blocks? Per the article, "a write to either file will cause some or all of the blocks to be duplicated." I have to think the bookkeeping involved in the former would be simpler and is more likely to be implemented as a prototype in a non-OCFS2 filesystem. At least in the short term.


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Re: Pity userspace on where this is done on a simple minded filesystem

Posted May 6, 2009 0:17 UTC (Wed) by adj (subscriber, #7401) [Link]

s/former/latter/ in the above.

Re: Pity userspace on where this is done on a simple minded filesystem

Posted May 6, 2009 0:57 UTC (Wed) by JoeBuck (guest, #2330) [Link]

But appending (to logs, for example) is such a common special case that it would be likely to be supported at an early stage, so that you have an efficient representation when you take a snapshot of a filesystem, and then you let it go on, appending lots of stuff to your log files, blocks belonging to a common prefix can be shared.

Re: Pity userspace on where this is done on a simple minded filesystem

Posted May 6, 2009 1:01 UTC (Wed) by corbet (editor, #1) [Link]

btrfs, at least, has COW wired pretty deeply into it. So it will only copy blocks which have actually been changed. Results on other filesystems may vary.


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