# Chunk size setting

**URL:** <https://kopia.discourse.group/t/chunk-size-setting/1351>\
**Category:** General\
**Created:** [August 15, 2022, 5:35pm UTC](https://kopia.discourse.group/t/chunk-size-setting/1351 "2022-08-15T17:35:55Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![mahikeulbody](https://avatars.discourse-cdn.com/v4/letter/m/77aa72/32.png) [@mahikeulbody](https://kopia.discourse.group/u/mahikeulbody)\
**Post date:** [August 15, 2022, 5:35pm UTC](https://kopia.discourse.group/t/chunk-size-setting/1351/1 "2022-08-15T17:35:55Z")

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Hi,

I have the following use case :

Each time I download on my PC a lot of new photos from my camera, I backup them immediately. Later, gradually, I set metadata on the photos (title, location, etc…). And then I backup them again.

The average size of my photos is 6-10MB.

With Borg I can set the chunk strategy so this new backup doesn’t increase the backup size so much. With Kopia, the backup size increases as if I had added new photos. In others words, if I modify the metadata of a 8MB photo, the backup size increases by 8MB.

Are there some evolutions planned on this topic ?

Thanks for any answer.

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**Author:** ![basldfalksjdf](https://avatars.discourse-cdn.com/v4/letter/b/ce73a5/32.png) [@basldfalksjdf](https://kopia.discourse.group/u/basldfalksjdf)\
**Post date:** [August 17, 2022, 12:52am UTC](https://kopia.discourse.group/t/chunk-size-setting/1351/2 "2022-08-17T00:52:28Z")

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> [@mahikeulbody](#):
>
> With Kopia, the backup size increases as if I had added new photos. In others words, if I modify the metadata of a 8MB photo, the backup size increases by 8MB.

This does not sound right. Kopia only backs up changed chunks. What splitter algorithm are you using with Kopia?

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**Author:** ![mahikeulbody](https://avatars.discourse-cdn.com/v4/letter/m/77aa72/32.png) [@mahikeulbody](https://kopia.discourse.group/u/mahikeulbody)\
**Post date:** [August 17, 2022, 5:34am UTC](https://kopia.discourse.group/t/chunk-size-setting/1351/3 "2022-08-17T05:34:29Z")

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> Kopia only backs up changed chunks.

Yes, but I suppose that if the chunk size is larger than my photo, it creates a new chunk, even if I have modified only a few Kbytes of metadata into the photo.

> What splitter algorithm are you using with Kopia ?

I don’t understand this question : I didn’t find any “splitter algorithm” choice into KopiaUI.

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**Author:** ![basldfalksjdf](https://avatars.discourse-cdn.com/v4/letter/b/ce73a5/32.png) [@basldfalksjdf](https://kopia.discourse.group/u/basldfalksjdf)\
**Post date:** [August 17, 2022, 7:47pm UTC](https://kopia.discourse.group/t/chunk-size-setting/1351/4 "2022-08-17T19:47:55Z")

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You can see the splitter algorithm option under `Repository`. It is set when you originally create a repository, so you likely are using `DYNAMIC-4M-BUZHASH` if you did not change it. You can change this to a smaller chunk size, but you will need to recreate the repository as far as I know. There are also performance tradeoffs with using smaller chunks (see the discussion at [Deduplication efficiency](https://kopia.discourse.group/t/deduplication-efficiency/1298)), but if most of your files are small, then you may benefit from a smaller chunk size.

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**Author:** ![mahikeulbody](https://avatars.discourse-cdn.com/v4/letter/m/77aa72/32.png) [@mahikeulbody](https://kopia.discourse.group/u/mahikeulbody)\
**Post date:** [August 17, 2022, 8:23pm UTC](https://kopia.discourse.group/t/chunk-size-setting/1351/5 "2022-08-17T20:23:21Z")

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Thank you very much for this answer !

I will try it.