A volume encryption status query may cause the server to freeze

View products that this article applies to.

Symptoms

Consider the following scenario:

You have a computer that is running Windows Server 2012 R2, Windows Server 2012, Windows Server 2008 R2, or Windows Server 2008.
The server has a large amount of I/O activity that results in several gigabytes' worth of changed data.
BitLocker (fveapi.dll) is not installed.
A requestor on the server queries the status of the encryption on the volume. For example a backup application queries this status.

In this scenario, you notice the following symptoms on the server:

I/O activity may stop.
The server may freeze.
If the Failover Clustering feature is installed on the server, you may receive a Stop error code 0x9E that resembles the following:
0x0000009E (parameter1, parameter2, parameter3, parameter4)
USER_MODE_HEALTH_MONITOR

Cause

This problem occurs because the BitLocker feature is not installed or enabled on the server. Because BitLocker's fveapi.dll is not installed, there is no ready cache for the volume encryption information. Therefore, the volume must have a raw (direct-access storage device [DASD]) read. This requires all the changed data to be flushed to the underlying storage to provide a consistent view of the raw file system.

↑ Back to the top

Workaround

To work around this problem, install the BitLocker feature on the server. (You do not have to configure BitLocker or encrypt any volume.) This adds a flag for BitLocker, and Fveapi.dll will enable the requestor of volume encryption status to retrieve a cached reply and therefore to avoid the expense of a raw (DASD) read of the file system.

↑ Back to the top