[OSM-dev] tiles at home disk usage

[Jeroen Dekkers]

At Wed, 2 May 2007 12:02:51 +0200,
Frederik Ramm wrote:
> 
> Oliver,
> 
> > Just as background info for anyone who doesn't watch munin stats:  
> > the sea and
> > coastline tiles have pushed us up to 92% disk space usage (from 57%  
> > before)
> > on tiles at home
> 
> Two questions on that.
> 
> First, if I sum up all sizes given in the latest.txt.gz file, I end  
> up with the number 502032007251339, that's roughly 500 GB. Do we  
> really have that amount of tile data, or is there something wrong  
> with either the file or my sum? From my calculations, the empty sea  
> tiles seem to make up only about 6 GB, but if 500 GB tile data is 92%  
> disk usage and you only had 57% before, then that means that not 6 GB  
> but 200 GB have been added recently.

Do you count the right column? I count 66GB. Here is a nice table:

                 layer 1         layer 2         layer 3           total
zoom  0           22,480               0          12,797          35,277
zoom  1           55,612               0          31,231          86,843
zoom  2          134,877               0          74,678         209,555
zoom  3          325,737               0         189,342         515,079
zoom  4          776,655               0         498,861       1,275,516
zoom  5        1,876,724               0       1,334,747       3,211,471
zoom  6        6,925,280               0       3,118,934      10,044,214
zoom  7       10,719,525               0       7,717,831      18,437,356
zoom  8       25,339,412               0      18,309,130      43,648,542
zoom  9       60,292,249               0      40,802,845     101,095,094
zoom 10      166,032,741               0     108,227,213     274,259,954
zoom 11      456,792,268               0     258,925,376     715,717,644
zoom 12      229,182,865         661,252     327,060,425     556,904,542
zoom 13      574,283,357       1,349,422     859,039,865   1,434,672,644
zoom 14    1,289,658,006       3,302,032   2,028,254,098   3,321,214,136
zoom 15    2,968,696,667       7,267,224   5,019,642,154   7,995,606,045
zoom 16    7,405,587,097      16,464,946  10,904,265,715  18,326,317,758
zoom 17   20,557,170,910      37,190,295  13,057,235,718  33,651,596,923
total     33,753,872,462      66,235,171  32,634,740,960  66,454,848,593

And here is a table for the number of tiles:

                 layer 1         layer 2         layer 3           total
zoom  0                1               0               1               2
zoom  1                4               0               4               8
zoom  2               16               0              16              32
zoom  3               64               0              64             128
zoom  4              256               0             256             512
zoom  5            1,024               0           1,024           2,048
zoom  6            4,096               0             156           4,252
zoom  7            1,348               0             624           1,972
zoom  8            5,270               0           2,496           7,766
zoom  9           21,077               0           9,984          31,061
zoom 10           84,312               0          39,936         124,248
zoom 11          337,223               0         159,744         496,967
zoom 12           59,434              39          63,081         122,554
zoom 13          159,725             122         151,029         310,876
zoom 14          453,553             388         358,092         812,033
zoom 15        1,339,015           1,144         854,981       2,195,140
zoom 16        4,195,982           3,155       2,055,509       6,254,646
zoom 17       14,131,388           7,802       3,232,215      17,371,405
total         20,793,788          12,650       6,929,212      27,735,650

> The empty sea tiles are, as far as I can think of, the only thing  
> that was really added by the new software. The coastal tiles were  
> there before, with a thin blue line for the coastline instead of a  
> blue area, which should not make a world of a difference in terms of  
> PNG file size.

A tile which is fully the same colour is 571 bytes. That can also be
green tiles from parks etc, but I guess most of them is water. I count
12,698,593 of them. That would be 6.5G in size. But if they have to be
stored in 512 bytes sectors, that would mean 1024 bytes of diskspace
used per tile, making it 13G in total.

I've attached the script to generate the numbers. It's quickly hacked
up and could use some refactoring however...

Jeroen Dekkers
-------------- next part --------------
A non-text attachment was scrubbed...
Name: tahstats.py
Type: application/octet-stream
Size: 1972 bytes
Desc: not available
URL: <http://lists.openstreetmap.org/pipermail/dev/attachments/20070502/74c1aedd/attachment.obj>