[Tilesathome] Deploying Map - Architecture planning

[Zsombor Szabó]

Hi t at h people,

I'm a newbie to OSM and I am thrilled to see that there exists such a  
project.
All things short, basically I want to deploy a map for mobile devices  
from OSM data with the following features:

- map tiles should be up to date (preferably they should change after  
K*hour if edited)
- map tiles should be smaller size than the default 256x256
- don't want to load OSM servers with heavy traffic
- want to have a high availability and scalable architecture

Looking through the documentation at http://wiki.openstreetmap.org/index.php/Deploying_your_own_Slippy_Map
it lead me to plan the following architecture:

- mobile devices will request maptiles from local sqlite database
- mobile devices will fallback to request maptiles from Amazon S3  
buckets if a maptile doesn't exist in the local sqlite database
- initialy all maptiles will be uploaded into the S3 buckets (to save  
space use oceantiles and emptyland(?))
- maptiles will be generated with a modified tilesGen.pl script on  
Amazon EC2 instances which will upload the maptiles into the S3 buckets
- the EC2 instances will check periodically (K*hour) for updated tiles  
through the OSM API call GET /api/0.5/changes?hours=[K*1]&zoom=[12-17]  
and they will render them and upload them to S3 buckets
- mobile devices request the timestamp of the tiles from the EC2  
instances while panning/zooming and compare them to their local  
maptiles' timestamps so they know when to request changed maptiles  
from S3

drawbacks:
- if for some reason the EC2 system/program will be out more than 24  
hours, the system will have to rerender all maptiles since the current  
OSM 0.5 API doesn't let request a time span larger than 24 hours at  
GET /api/0.5/changes
- the map's look and feel is not so slick than the one rendered with  
Mapnik

Any remarks, observations appreciated.

Question: How many gigabytes is currently the world with t at h tiles?

Regards,
Zsombor Szabo