impact of "Disable Sparse Files"?


I’m kinda familiar with the concept of sparse files, when it goes to reserve space in advance on a drive for files to be created.

I’m unsure, what influences they have in the syncthing context.

Why are sparse files enabled by default for each share?

Will the disabling of sparse files for a share (or for all shares) have any impact in speed / resources of a syncthing client ?

What about the creation of sparse files for thousands of thousands of small files, or huge files? or files, that change very often?

Will enabling sparse files affect the speed of syncing? or affect the disk utilization in a “stressful” way?

Any thoughts or facts ?

Thank you.

(I only found this topic/post)

With sparse files disabled Syncthing will write out blocks full of zeroes. With it enabled it will just skip writing zero blocks, leaving the file sparse. This is more efficient, when supported and when you have files full of zeroes… if you don’t, it doesn’t matter.


Anyone has an example or an producive usercase, why anybody shoud have files filled with zeroes?

Probably most commonly, VM/disk images.

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Memory mapped files, where a file is used as a memory region. For a two-dimensional array, for example, and where only a part of the array is filled.

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