Startup RAM is the amount of memory that a virtual machine (VM) is configured to use when it's powered on. It's the initial memory allocation defined in the VM's configuration settings.
Key Aspects of Startup RAM
- Initial Memory Allocation: It specifies the memory available to the VM when it starts.
- Configuration Setting: This value is set in the VM's configuration, typically within the settings related to memory allocation.
- Static Allocation (Initially): Even if dynamic memory is enabled, the startup RAM is the base amount the VM begins with. Dynamic memory allows the VM to use more RAM if needed (up to a configured maximum), but it won't go below the startup RAM value.
- No Automatic Reduction: Unlike dynamic memory, the startup RAM doesn't automatically decrease. The VM always has at least this amount of RAM available.
Startup RAM vs. Dynamic Memory
While startup RAM provides the initial memory allocation, dynamic memory (if enabled) allows the VM to adjust its memory usage based on demand, within specified limits. The startup RAM acts as the floor for this dynamic allocation. If the VM needs more memory, it can request it (up to a pre-defined limit). When the demand decreases, the memory can be released (but not below the startup RAM value).
Example Scenario
Imagine you configure a virtual machine with 4GB of startup RAM and enable dynamic memory with a maximum allocation of 8GB.
- When the VM starts, it will have 4GB of RAM allocated.
- If the applications running on the VM require more memory, the VM can request more, up to a total of 8GB.
- If the applications no longer need the extra memory, the VM can release it back to the hypervisor, but it will always retain the initial 4GB defined by the startup RAM setting.
In essence, startup RAM provides a guaranteed minimum amount of memory, while dynamic memory provides flexibility to adjust memory allocation as needed.
