GIS Servers and the 64-bit Question
general, mapserver, opinion
The following is the first in a series of posts related to configuring a 64-bit Windows server as a GIS server using MapServer and Python.
Why move to 64-bit?
If a server’s operating system and hardware are 64-bit it seems a waste not to take advantage of them. It may be better to look at the question why move to 64-bit software, as why wouldn’t you move to 64-bit software?
Its nice to be able to claim one-upmanship over commercial GIS products who are only now bringing out 64 bit versions. However having gone through the pain of setting up Open Source GIS applications on Windows I’m not surprised companies took the time to simplify the process (and wait for Microsoft to do some of the legwork) rather than dealing with all the 32/64 bit support issues too early.
Memory & Performance
Performance-wise one of the main benefits of 64-bit hardware is the extra memory you can add to a server. 64 bit Windows 7 can support up to 128 GB of RAM. GIS applications are used to dealing with large spatial datasets ?” both raster and vector, and will therefore be able to make full use of additional memory. This is not the case for all programs for example Visual Studio which is unlikely to be multiuser or used to handle large datasets.
A 64-bit server allows files larger than 4GB to be loaded directly into memory. This is very advantageous to video editing, bit also to GISs that use aerial imagery which can be served more quickly if loaded into memory rather than loading in sections.
Databases make use of additional memory to cache data for faster responses to user requests, and to handle more concurrent connections ?” there is a nice summary post on the benefits of 64-bit for SQL Server here. Spatial databases, with their additional larger and complex data structures, are even better placed to take advantage of 64-bit computing.
Even though it is not the easiest thing to configure a GIS server, nearly all future software will have a 64 bit release, and in a few years 32 bit versions may start to be phased out. Future-proofing a system currently in development may help your GIS to last a few more years in a production environment.
Another benefit is that you can start designing your infrastructure to scale ?” all on the same physical machine. You can create a virtual web server, a virtual database server, and a virtual map server and divide up large amounts of memory, facilitated by a 64-bit architecture, between them. If the site needs to allow for more users, you can simply take the virtual server and move it to another physical machine ?” and (in theory) there is very little to configure once the virtual machine has been moved.
As noted above the reduced number of physical machines should mean lower maintenance costs. In addition if you can get more throughput from your database then this may require fewer licences (such as for SQL Server 2008 which often comes with a per-processor licence). Of course with a 64-bit server you could have up to 64 processors, although this could well melt the server’s case..
What to Update?
I’m currently involved in a couple of projects, one using Windows Server 2008 and another Windows Server 2003. Both are 64-bit operating systems on 64-bit hardware. As 32-bit and 64-bit applications don’t play very well together it seems it will be an “all or nothing” migration, involving the following components:
Python (for TileCache and Mapscript)
I’ll try and put steps together for each of these for my future sanity, and also in the help that there will be a few more developers straddling the Open Source and Windows divide. It would be nice at the end to post some benchmarks, but running both set ups on the same server could prove problematictraumatic. If anyone has noticed performance increases when using 64-bit GIS applications please leave comments!