BE2012 SP1A Vmware agent backup via SAN mode is very slow

When backup of ESX virtual machines from BE 2012 server using SAN Mode . The backup through will be slow down till 5mb/sec and 1 TB data size backup took more than 1 day still unable to complete.

Below is the debug log error found on the vmware agent . VAAI.

[4844] 2013-01-15T22:48:54.392 [fsys\shared]        - VDDK-Log: diskLibPlugin: 2013-01-15T22:48:54.392+08:00 [04844 error 'Default'] Incomplete read from, Wanted 4718592 Got 0

[4844] 2013-01-15T22:48:56.405 [fsys\shared]        - VDDK-Log: diskLibPlugin: 2013-01-15T22:48:56.405+08:00 [04844 error 'Default'] Incomplete read from, Wanted 4718592 Got 0

[4844] 2013-01-15T22:48:58.230 [fsys\shared]        - VDDK-Log: diskLibPlugin: 2013-01-15T22:48:58.230+08:00 [04844 error 'Default'] Incomplete read from, Wanted 4718592 Got 0

[4844] 2013-01-15T22:49:00.039 [fsys\shared]        - VDDK-Log: diskLibPlugin: 2013-01-15T22:49:00.039+08:00 [04844 error 'Default'] Incomplete read from, Wanted 4718592 Got 0

[4844] 2013-01-15T22:49:02.177 [fsys\shared]        - VDDK-Log: diskLibPlugin: 2013-01-15T22:49:02.177+08:00 [04844 error 'Default'] Incomplete read from, Wanted 4718592 Got 0

[4844] 2013-01-15T22:49:04.673 [fsys\shared]        - VDDK-Log: diskLibPlugin: 2013-01-15T22:49:04.673+08:00 [04844 error 'Default'] Incomplete read from, Wanted 4718592 Got 0

[4844] 2013-01-15T22:49:08.994 [fsys\shared]        - VDDK-Log: diskLibPlugin: 2013-01-15T22:49:08.994+08:00 [04844 error 'Default'] Incomplete read from, Wanted 4718592 Got 0

[0228] 2013-01-16T19:08:17.391 [fsys\vmvcb]         - getFileRecord: Failed to find MFT record (29418) in cache, fetching from VMDK

[0228] 2013-01-16T19:08:17.391 [fsys\vmvcb]         - getFileRecord: Failed to find MFT record (30431) in cache, fetching from VMDK

[0228] 2013-01-16T19:08:17.391 [fsys\vmvcb]         - getFileRecord: Failed to find MFT record (43342) in cache, fetching from VMDK

[0228] 2013-01-16T19:08:17.406 [fsys\vmvcb]         - getFileRecord: Failed to find MFT record (41752) in cache, fetching from VMDK

[0228] 2013-01-16T19:08:17.406 [fsys\vmvcb]         - getFileRecord: Failed to find MFT record (36500) in cache, fetching from VMDK