@DCR, As MongoDB 3.6 officialy released as on dated 5th December 2017. For Testing environment i have deployed
MongoDB 3.6 in my environment. There is two new things i got in MongoDB 3.6 , which i have noticed. When we are starting the
1)The file system cache of this machine is configured to be greater
than 40% of the total memory
2)Starting in MongoDB 3.6, mongod bind to localhost (127.0.0.1) by
default. See Default Bind to Localhost.
Even in my Environment the test system setup configuration is
windows 10 enterprise with 64-bit
HDD is 500 GB
MongoDB version is 3.6
RAM is 4 GB
Note : The
--wiredTigerCacheSizeGB limits the size of the
WiredTiger internal cache. The operating system will use the available free memory for filesystem cache, which allows the compressed MongoDB data files to stay in memory. In addition, the operating system will use any free RAM to buffer file system blocks and file system cache.
To accommodate the additional consumers of RAM, you may have to decrease WiredTiger internal cache size.
@DCR, Even in my environment i am also getting the same message after running the
mongod server. It's nothing but a cache warning message which comes from
wiredTiger storage engine.
I am also uploading the screen shot below
As per MongoDB jira Blog Add warning about Windows SystemFileCacheSize for WiredTiger Some MongoDB users on Windows have switched to enabling
direct_io because the file system cache on Windows is greedy by default and can lead to content in allocated memory getting swapped out - which leads to terrible performance.
Windows provides the SetSystemFileCacheSize API that allows limiting the amount of memory that can be used by the file system cache. The setting is global across the computer.
We could add code into MongoDB that calls the API, and limits the amount of memory the file system cache can use to a percentage of available memory.
The call should only be done for storage engines that have a cache management layer.
MMAP relies on the file system cache using all available memory - limiting how much memory is available would hurt
As starting in MongoDB 3.0, the WiredTiger storage engine is available in the 64-bit builds. Changed in version 3.2: The WiredTiger storage engine is the default storage engine starting in
For further your ref Here , Here and WiredTiger storage engine