[GRASS-user] Splitting a location across several disks

[Glynn Clements]

Dylan Beaudette wrote:

> It has been a while, but glad to be back on GRASS-user.
> 
> I am working on a project that involves a significant storage dilemma: try
> and fit most of the files into a 500 Gb SSD for blazing-fast I/O, or fall
> back to a standard but higher capacity disk drive.
> 
> Would it be possible to store "derived" data into a mapset that is on
> standard disk, while the "source" data reside in another mapset, stored on
> the SSD?
> 
> In other words, is it OK for a location to contain several mapsets that
> don't "live" on the same physical disk. It seems like it should work (via
> symlink), but I would like to see if there are any caveats that I should be
> aware of.

If symlinks don't work, Linux supports "mount --bind ...", which lets
you mount a directory from an already-mounted filesystem at another
location. Windows has similar features (e.g. reparse points), although
I'm not that familiar with the specifics.

The main constraint is that you can't split a single mapset across
devices, as it must be possible to rename() files in the .tmp
subdirectory to other directories withing the mapset, which requires
that they are on the same physical partition (rename() only
manipulates directory entries, it won't move the file's data blocks).

-- 
Glynn Clements <glynn at gclements.plus.com>