Accelerator does not support writing the same image to two storage units at the same time

Problem

When an accelerator backup is initiated via a Storage Lifecycle Policy (SLP) with a second copy configured, the second copy will fail with status 84 (media write error):

Error Message

========================= Job Details =================================

8/04/2015 10:01:30 PM - Critical bptm(pid=6436) include image failed         
8/04/2015 10:01:30 PM - Critical bptm(pid=6436) image write failed: error 2060001: one or more invalid arguments  
8/04/2015 10:01:34 PM - Error bptm(pid=6436) cannot write image to disk, Invalid argument
8/04/2015 10:01:34 PM - Error bptm(pid=6436) INF - media write error (84), cannot continue with copy 2

==================================================================

The policy editing screen will explicitly disallow multiple copies for this reason, by greying out the 'multiple copies' section:

The bptm log will show storage server errors 2060001 and 2060053, as shown below from a bptm log at verbose level 5:

===========================BPTM (Verbose 5)================================

15:15:38.940 [4444.892] <16> 1691488:bptm:4444:<hostname>: libsts openp() 15/04/09 15:15:38: stsm_open_module D:\VERITAS\NetBackup\bin\\ost-plugins\libstspizapi.dll failed err 2060053 platerr 193: LoadLibrary failed
15:21:38.257 [4444.892] <16> write_data: cannot write image to disk, Invalid argument
15:21:38.257 [4444.892] <2> set_job_details: Tfile (1691487): LOG 1428564098 16 bptm 4444 INF - media write error (84), cannot continue with copy 2
15:21:38.257 [4444.892] <2> send_job_file: job ID 1691487, ftype = 3 msg len = 86, msg = LOG 1428564098 16 bptm 4444 INF - media write error (84), cannot continue with copy 2
15:21:38.335 [4444.892] <16> terminate_twin: INF - media write error (84), cannot continue with copy 2

=========================================================================

Cause

Accelerator does not support writing the same image to two storage units at the same time (inline copy). This is enforced in the policy editing screen of the NetBackup GUI, and the interface will not permit selection of both Accelerator and multiple copies (in the schedule dialog).

If the policy is sent to a SLP with multiple backup destinations, NetBackup will write two accelerated copies at the same time to different storage units.  Subsequent full backups will fail the second copy when trying to retrieve previous backup include data. 

Solution

Writing multiple copies of accelerator-enabled backups to storage servers is currently not supported in NetBackup.