On 05/25/16 02:29, Hugo Mills wrote:
> On Wed, May 25, 2016 at 01:58:15AM -0700, H. Peter Anvin wrote:
>> Hi,
>>
>> I'm looking at using a btrfs with snapshots to implement a generational
>> backup capacity. However, doing it the naïve way would have the side
>> effect that for a file that has been partially modified, after
>> snapshotting the file would be written with *mostly* the same data. How
>> does btrfs' COW algorithm deal with that? If necessary I might want to
>> write some smarter user space utilities for this.
>
> Sounds like it might be a job for one of the dedup tools
> (deupremove, bedup), or, if you're writing your own, the safe
> deduplication ioctl which underlies those tools.
>
I guess I would prefer if data wasn't first duplicated and then
deduplicated if possible. It sounds like I ought to write a "smart
copy-overwrite" tool for this.
-hpa
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