Comment # 5 on bug 1149148 from Arvin Schnell

(In reply to Kai Dupke from comment #4)
> (In reply to Arvin Schnell from comment #3)
> > Depends on what is reasonable. It will likely need research for every
> > filesystem.
> 
> I wonder if this has to be a factor, or if a fixed amount (i.e. 250GB) would
> do as well.

Likely not a good idea, e.g. for an almost empty 200 GiB filesystem.

> > Another problem is that the maximal size for ext4 is set to 16 TiB. This
> > is done since ext4 needs the 64bit feature to handle larger devices
> > (https://www.netways.de/blog/2017/12/13/how-to-use-ext4-beyond-16tib/).
> > E.g. an ext4 normally created on SLE12 SP3 cannot be grown beyond 16 TiB.
> > So strictly speaking the 64bit feature must be checked (using dumpe2fs).
> 
> In the shrinking case, this can't be an issue, can it be? In case a size
> bigger then 16TB, 64bit must be already enabled, right? So shrinking does
> not need to check this flag.

The library provides the possible range for resizing. For the range to
be correct the flag is needed and that was the use-case I had in mind.

> I wonder if it is checked for extending, but at least for openSUSE I am not
> aware of any notice when I extended a FS beyond 16TB (this system alone has
> 2 FS > 16TB) resp. created a FS that big.

The libstorage provides the maximal allowed value for a FS. Whether the
UI code uses it I cannot say.

BTW: The resize operation might have to move several TiB on the disk. That
could take several hours.