Re: [ANNOUNCE] mini_fo-0.6.0 overlay file system

[Markus Klotzbuecher]

On Thu, May 12, 2005 at 11:18:36PM -0400, Kyle Moffett wrote:

> 2) When forced to copy data, the copy should be done in the context of
> whatever process is doing the "write" operation, and be interruptible,
> etc.  The end result is that if you union an nfs mount over another one,
> it will just seem like a write to a big file takes a _really_ long time
> to complete.

This is what happens with mini_fo, provided your kernel is preemptive.

> 3) ext2/3 should get an extra flag for files and directories that
> indicates nonresidence.  This would be used by the VFS union layer to
[...]

I like the idea of copying modified data on a per block basis. This
really would avoid unnecessary long copy operations and potentially
save a lot of storage. But I think a unifying layer should not rely on
specialities such as sparse files or flags provided by the lower layer
file systems.

Markus
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