[GRASS-user] syncing two locations

M S mseibel at gmail.com
Wed May 28 08:26:30 EDT 2008

I completely agree to use your approach, with the shared location with
multiple mapsets.  Using something like Unison sync's the locations
well, but has problems with single file reconciliation such as an
sqlite.db file for all the vector attributes.  Now I have some vector
files that dont have attributes.  :-(

It seems to work fine for rasters, but cant say for absolute.  I would
stick with your approach, or use the linux clustering approach like
you mentioned.

thanks for the feedback, this will be a great help to distribute the
processing load.


On 5/22/08, Markus Neteler <neteler at osgeo.org> wrote:
> (I take liberty to cc the list again for discussion)
> On Thu, May 22, 2008 at 3:59 PM, M S <mseibel at gmail.com> wrote:
>> That is cool.  I will definitely check out the wiki page.
>> Perhaps I am not using locations or more specifically mapsets as
>> efficiently as I could be.  If I were to use a single location, but
>> with different mapsets, would there be issues with changing the region
>> boundary and/or the cell resolution?
> not at all, all mapsets are independent.
>> For example, in my main area of interest (basin) there were areas I
>> needed to do finer detailed analysis, going from 25 foot cells to 3
>> foot cells (r.in.xyz + r.report helped me find this optimal cell size,
>> great stuff!), would this be an issue within the same location, but
>> using a different mapset?  I had thought that region settings applied
>> to a location.
> no :) to a mapset!
> I have added
> http://grass.osgeo.org/wiki/Parallel_GRASS_jobs#Background
>> I had (perhaps not the best choice, copied the location to another
>> workstation) and changed the region resolution and boundary, and then
>> ran more detailed analysis.
> If you do it serially, no problem. Otherwise it will conflict.
>> Under this scenario, does it still make sense to use a single shared
>> location?
> Most likely.
>> One problem I foresee is with vectors using a single
>> sqlite.db file,
> That's true. You cannot write simultaneously to the same sqlite.db file.
> http://en.wikipedia.org/wiki/SQLite
> "A write access can only be satisfied if no other accesses are
> currently being serviced, otherwise the write access fails with an
> error code (or can automatically be retried until a configurable
> timeout expires). This concurrent access situation would change when
> dealing with temporary tables.
> "
> But just use different names, so multiple sqlite.db files?
>> in two different locations and then getting the vector
>> database out of sync, and unable to rectify this with syncing the
>> locations.  It seems that reprojecting the data into the location is
>> one way to deal with this single DB issue.
> I feel that it's making things worse.
>> Most all of what I'm doing
>> is time-consuming raster analysis though, and on the first sync,
>> things seemed to work as expected.
> OK fine.
> Please let's collect ideas in the wiki how to deal with vector data
> and related DBs when processing in parallel.
> Markus
>> Mark
>> On 5/21/08, Markus Neteler <neteler at osgeo.org> wrote:
>>> On Wed, May 21, 2008 at 5:58 PM, M S <mseibel at gmail.com> wrote:
>>>> I have two GRASS workstations performing various lidar and basin
>>>> operations.  My idea was to distribute the processing on various
>>>> machines.
>>>> As new data gets created in each location on each computer, when all
>>>> processes are done, I would like to re-sync the locations to be the
>>>> same.
>>> I did massive MODIS map processing on a cluster and used
>>> one location only in a shared network directory. Therein multiple
>>> mapsets with a final g.copy job to the mapset keeping the results.
>>> I have documented it here:
>>> http://grass.osgeo.org/wiki/Parallel_GRASS_jobs#PBS
>>> Markus
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