[Talk-GB] Technical Help

[Paul Norman]

On 10/28/2016 5:28 AM, Brian Prangle wrote:
>
> There's a small amount of seed funding and we need to size a server 
> and storage that will serve OSM tiles for the West Midlands 
> (Geofabrik's download is 37MB for an osm.pbf file). We would need a 
> production server with an initial guesstimate hit rate of 5000 per day 
> and a dev server, and a backup for both.

Some ballpark estimates

Disk: Both the rendering data and slim data (if doing daily updates with 
change files) are each about 8x PBF size. Add more for tile caching and 
you probably want 4-8GB of space to be safe. Any VM you get will have 
this. You don't need it with enough RAM and such a small DB, but SSD 
storage is a plus.

Ram: 2GB minimum. If you only have 1GB you have to worry about how much 
the OS is consuming. This lets everything be in memory.

CPU: Depends on how concurrent the peak load, caching, how fresh the 
tiles need to be, etc. I'd go with at least 2 threads or cores. On 
average you need less, but a single user can easily cause enough load 
that you want 2+ metatiles to be rendered at once

5000 hits per day is probably in the ballpark of 5 tiles per second 
peak. It all depends on how spread out the load is, how many tiles per 
hit, etc. A modern CPU can render 1 metatile (64 tiles) in one second 
per CPU thread. Faster in your case with a smaller database.

I recommend having both production servers running and splitting the 
load between them so their caches remain up to date.

You want to consider

- How old you allow data to become
- How old are the tiles you are prepared to serve
- If you plan to update daily from geofabrik diffs or to reload the 
database completely

If you were purchasing physical hardware I'd recommend considering CPU 
requirements more carefully, but since you're almost certainly using 
VMs, it might be better to start testing.