• Logon time very high for end users.
• Targets responding slowly in session.
• Users intermittently unable to login.

The recommendation to mitigate this is to move the Write Cache away from the PVS Server itself and place the processing overhead at the target device instead.

Problem Cause

When each Target Device boots up the OS is not aware of the Write Cache and writes to the logical disk that it is presented (the vDisk). The PVS driver then redirects this data at the block level to the write cache which in your environment is held on the PVS server.

When our BNIStack driver (our transport stack for communicating with the PVS server) is then initialized,  it will pull down chunks of the vDisk as and when they are needed from your vDisk store which is on your PVS server also. The BNIStack driver will also access the write cache directly when it needs to issue additional writes from the target device.  The communication in relation to the above is carried out between the BNIStack driver on the target device and the Stream Service on the PVS server.

The Target Device BNIStack driver is also responsible for retries (because UDP does not). The base timeout for a packet timeout is 10 seconds. If the server responds quickly, this value is reduced by half all the way down to 1 second.

Correspondingly, if the server responds slowly the timeout will double all the way up to 10 seconds.

A retry timeout of 1 second or less may cause excessive I/O retries, leading to slow response and hanging of target devices which will then ultimately lead to a stream service failure.