VMware backups failing with status code 6/23

Hi everyone,

I have two VMs use the same datastore. I create VMware backup job for each of them with san transport type. VM1 backup succesfully but VM2 is not.

VM1 is a application server, total data is about 50G

VM2 is a file server, total datasize is about 2TB

backup job on VM2 fail once there is an error with "Map disk region" appear on vCenter.

detail logs of VM2:

3/28/2015 9:12:47 PM - Info nbjm(pid=6008) starting backup job (jobid=1851) for client VM2, policy file5, schedule Full  
3/28/2015 9:12:47 PM - estimated 0 Kbytes needed
3/28/2015 9:12:47 PM - Info nbjm(pid=6008) started backup (backupid=VM2_1427551967) job for client VM2, policy file5, schedule Full on storage unit mediaserver-hcart3-robot-tld-0
3/28/2015 9:12:47 PM - started process bpbrm (26331)
3/28/2015 9:12:48 PM - connecting
3/28/2015 9:12:48 PM - connected; connect time: 0:00:00
3/28/2015 9:12:49 PM - mounting PEP041
3/28/2015 9:13:43 PM - mounted; mount time: 0:00:54
3/28/2015 9:13:43 PM - positioning PEP041 to file 1
3/28/2015 9:13:50 PM - positioned PEP041; position time: 0:00:07
3/28/2015 9:13:50 PM - begin writing
3/28/2015 9:20:26 PM - end writing; write time: 0:06:36
3/29/2015 4:11:45 AM - Info bpbrm(pid=26331) VM2 is the host to backup data from     
3/29/2015 4:11:45 AM - Info bpbrm(pid=26331) reading file list for client        
3/29/2015 4:11:45 AM - Info bpbrm(pid=26331) starting bpbkar on client         
3/29/2015 4:11:45 AM - Info bpbkar(pid=26334) Backup started           
3/29/2015 4:11:45 AM - Info bpbrm(pid=26331) bptm pid: 26335          
3/29/2015 4:11:45 AM - Info bptm(pid=26335) start            
3/29/2015 4:11:46 AM - Info bptm(pid=26335) using 65536 data buffer size        
3/29/2015 4:11:46 AM - Info bptm(pid=26335) using 30 data buffers         
3/29/2015 4:11:46 AM - Info bptm(pid=26335) start backup           
3/29/2015 4:11:46 AM - Info bptm(pid=26335) Waiting for mount of media id PEP041 (copy 1) on server mediaserver. 
3/29/2015 4:12:40 AM - Info bptm(pid=26335) media id PEP041 mounted on drive index 2, drivepath /dev/nst2, drivename HP.ULTRIUM6-SCSI.002, copy 1
3/29/2015 4:18:58 AM - Error bpbrm(pid=26331) from client VM2: ERR - Error opening the snapshot disks using given transport mode: Status 23
3/29/2015 4:18:59 AM - Critical bpbrm(pid=26331) from client VM2: FTL - cleanup() failed, status 6    
3/29/2015 4:19:01 AM - Error bptm(pid=26335) media manager terminated by parent process       
3/29/2015 4:19:23 AM - Info bpbkar(pid=0) done. status: 6: the backup failed to back up the requested files 
the backup failed to back up the requested files(6)

VM1:

3/28/2015 9:35:34 PM - Info nbjm(pid=6008) starting backup job (jobid=1854) for client VM1, policy CAS3, schedule Full  
3/28/2015 9:35:34 PM - estimated 0 Kbytes needed
3/28/2015 9:35:34 PM - Info nbjm(pid=6008) started backup (backupid=VM1_1427553334) job for client VM1, policy CAS3, schedule Full on storage unit mediaserver-hcart3-robot-tld-0
3/28/2015 9:35:34 PM - started process bpbrm (22379)
3/28/2015 9:35:35 PM - connecting
3/28/2015 9:35:35 PM - connected; connect time: 0:00:00
3/28/2015 9:35:36 PM - mounting PEP042
3/28/2015 9:36:27 PM - mounted; mount time: 0:00:51
3/28/2015 9:36:27 PM - positioning PEP042 to file 1
3/28/2015 9:36:34 PM - positioned PEP042; position time: 0:00:07
3/28/2015 9:36:34 PM - begin writing
3/28/2015 9:40:59 PM - end writing; write time: 0:04:25
3/29/2015 4:34:32 AM - Info bpbrm(pid=22379) VM1 is the host to backup data from     
3/29/2015 4:34:32 AM - Info bpbrm(pid=22379) reading file list for client        
3/29/2015 4:34:32 AM - Info bpbrm(pid=22379) starting bpbkar on client         
3/29/2015 4:34:32 AM - Info bpbkar(pid=22382) Backup started           
3/29/2015 4:34:32 AM - Info bpbrm(pid=22379) bptm pid: 22383          
3/29/2015 4:34:32 AM - Info bptm(pid=22383) start            
3/29/2015 4:34:33 AM - Info bptm(pid=22383) using 65536 data buffer size        
3/29/2015 4:34:33 AM - Info bptm(pid=22383) using 30 data buffers         
3/29/2015 4:34:33 AM - Info bptm(pid=22383) start backup           
3/29/2015 4:34:33 AM - Info bptm(pid=22383) Waiting for mount of media id PEP042 (copy 1) on server mediaserver. 
3/29/2015 4:35:23 AM - Info bptm(pid=22383) media id PEP042 mounted on drive index 3, drivepath /dev/nst4, drivename HP.ULTRIUM6-SCSI.003, copy 1
3/29/2015 4:35:58 AM - Info bpbkar(pid=22382) INF - Transport Type =  san      
3/29/2015 4:39:36 AM - Info bpbkar(pid=22382) bpbkar waited 27259 times for empty buffer, delayed 51434 times   
3/29/2015 4:39:36 AM - Info bptm(pid=22383) waited for full buffer 4763 times, delayed 6489 times    
3/29/2015 4:39:55 AM - Info bptm(pid=22383) EXITING with status 0 <----------        
3/29/2015 4:39:55 AM - Info bpbrm(pid=22379) validating image for client VM1        
3/29/2015 4:39:56 AM - Info bpbkar(pid=22382) done. status: 0: the requested operation was successfully completed    
the requested operation was successfully completed(0)

Please help me to solve this issue.

Thank you.

Tuan.