Why is access to a GFS file system slower right after its mounted?
The first access after a GFS mount will be slower because GFS needs to read in the resource group index and resource groups (internal GFS data structures) from disk. Once they’re in memory, subsequent access to the file system will be faster. This should only happen right after the file system is mounted. It also takes additional time to read in from disk: (1) the inodes for the root directory, (2) the journal index, (3) the root directory entries and other internal data structures. You should be aware of this when performance testing GFS. For example, if you want to test the performance of the “df” command, the first “df” after a mount will be a lot slower than subsequent “df” commands.
The first access after a GFS mount will be slower because GFS needs to read in the resource group index and resource groups (internal GFS data structures) from disk. Once they’re in memory, subsequent access to the file system will be faster. This should only happen right after the file system is mounted.
