If you want a highly available GIS server deployment, your map and image caches also need to be highly available. To achieve this, the ArcGIS Server administrator can do one of the following:
- Place the site cache directory on a highly available file share.
- Configure cache directories on individual machines in a multimachine GIS server.
You can configure cache directories on each machine to make the caches highly available in a cloud GIS server deployment. You can use either option for on-premises deployments.
Use a highly available file share
For your on-premises GIS server site cache, you can designate a directory on a highly available file server that uses a Storage Area Network (SAN) or highly available Network Attached Storage (NAS). This is usually configured by your information technology staff.
If your organization has a SAN or NAS with sufficient space for your cache, this will be the easiest and most reliable solution to make your map and image caches highly available.
If you do not have access to such a file server, you can create cache directories on each machine in your deployment as described in the following section.
For highly available systems, you can backup your cache directories in cloud stores. Keep in mind that end users of map or image service caches may experience a performance penalty as tiles are retrieved from a cloud store compared to tile retrieval from a local disk. Also, ensure caches stored in cloud stores use compact v2 storage format.
Place cache directories on each machine in the deployment
Storing multiple copies of map and image caches on all machines in the site allows the cache and service to be highly available. Create directories on each machine in the GIS server site and copy all caches to each of these directories. All machines participating in the GIS server site must have access to every cache directory.
Be aware of the following when configuring local cache directories:
- You cannot use on-demand map caching with services configured with a local cache directory.
- Geoprocessing tools that update existing caches output to a common site cache directory. If you run these tools, you must move caches to the local cache directories of each machine participating in the GIS server.
Although there is more administrative overhead when implementing cache directories on every machine in the GIS server site, it is the only option when implementing a highly available GIS server in the cloud.
You can also implement this solution in on-premises deployments. This is recommended if you do not have a highly available file server available and your caches are not frequently (or never) updated.
By default, map and image caches are written to a single site cache directory. Follow these steps to configure cache directories on each machine participating in the GIS server site:
- Open the ArcGIS service endpoint of the server cache directory. The URL is in the format http://gisserver.domain.com:6080/arcgis/admin/system/directories.
- Choose the site cache.
- Click Edit.
- Set Use Local Directory to TRUE.
- Specify the path to a local cache directory. Cache directories must be created in the same place on all machines.
Once set, ArcGIS Server creates caches for map and image services published to that machine in the local cache directory you specified.
- Manually copy existing cache data from the site cache directory to each local cache directory.
Be sure the existing cache has finished building before attempting to copy it.
You can use rsync to move the cache, for example
rsync –avx -progress <login>@<location of existing cache> <local cache directory>