In this topic:
Virtual Disks for write caching overview
Changing Virtual Disk Settings to disable/enable write caching for a virtual disk
DataCore Server and Server Group States for server write caching states
About UPS Support
This software registers with the Windows® operating system to receive power events from the operating system. If the operating system knows the state of the UPS, then it is operating system compliant. UPS support in this software is dependent on the Windows operating system recognizing that a compliant uninterruptible power supply (UPS) is attached to the DataCore Server and that the UPS software will communicate events and states to the operating system. (This software does not support UPSs that are non-compliant to Windows operating system, but see the section Notes on Non-Compliant UPS for important information.)
If the UPS is operating system compliant, a battery icon will be displayed in the system tray.
If the DataCore Server is attached to any compliant UPS (as defined above), no additional setup is required; the support runs automatically. UPS power states are monitored from the Windows operating system and reported in the software.
When line power goes off and the UPS takes over, write caching is automatically disabled, which allows all write operations from hosts to be written directly to the back-end storage and then acknowledged.
When line power is restored and the server is no longer running on battery backup, write caching is automatically enabled again.
Alerts are generated when the server goes on UPS battery backup or when the low battery state is reached.
When the low battery state is reached, the server will be stopped in order to ensure a graceful shutdown. (When a server is stopped, DataCore device drivers are stopped and active paths for mirrored virtual disks will failover to the other server in the server group.) The threshold setting forlow batterycan be adjusted in WindowsPower Options.Use caution when selecting this threshold. (Refer to Windows documentation for more information on Power Options.)
If the DataCore Server is restarted or powered on while having a power state of low battery, the server will come up stopped. However, the server can be manually started.
UPS Power States
The UPS power state and write caching state is displayed in the DataCore Server Details page>Info tab for each server. Power states are reported from the Windows operating system.
The UPS is plugged in and AC power is available.
Write caching is enabled.
AC line power unavailable
Write caching is disabled.
The UPS battery has reached the low power definition as set in Windows Power Options. Set Low Battery Action to "Shut down".
The state is unknown. This state could be reported because the DataCore Executive (Dcsx.exe) service is stopped, the server is down, or there is a network issue.
A non-compliant UPS is a UPS that are not connected to the Windows® operating system. When a UPS is used that is non-compliant with the Windows operating system, SANsymphony software is unable to monitor the UPS power state. (If the UPS is compliant, a battery icon will be displayed in the system tray.)
- When AC line power is unavailable, run the DataCore CmdletDisable-DcsServerWriteCache for each server that has lost power to disable write caching. This allows all write operations from hosts to be written directly to the back-end.
- If power is restored before the UPS reaches a low battery indication, then run the DataCore CmdletEnable-DcsServerWriteCache for each server to enable write caching.
- If a low battery indication is reached, stop virtualization on the DataCore Servers in order to ensure a graceful shutdown. When a server is stopped, DataCore device drivers are stopped and active paths for mirrored virtual disks will failover to the other server in the server group. (For compliant UPSs, this will happen automatically.) Virtualization can be stopped in the SANsymphony Management Consoleor by running the DataCore Cmdlet Stop-DcsServer.
- If the DataCore Server is restarted or powered on while having a power state of low battery, the server will come up stopped. However, the server can be manually started in the SANsymphony Management Console. After the restart, write caching will be enabled again. Virtualization can be started in the SANsymphony Management Console or by running the DataCore CmdletStart-DcsServer.