This patch should hold jobs in the Director's start queue if
 more than one simultaneous backup job wants to use the same
 Storage device with two different Pools (i.e. 2 Volumes).
 Apply the patch to version 1.36.1 with:

 cd <bacula-source>
 patch -p0 <1.36.1-pool.patch
 make
 make install
 ...

Index: src/dird/jobq.c
===================================================================
RCS file: /cvsroot/bacula/bacula/src/dird/jobq.c,v
retrieving revision 1.25
retrieving revision 1.26
diff -u -r1.25 -r1.26
--- src/dird/jobq.c	24 Sep 2004 12:30:14 -0000	1.25
+++ src/dird/jobq.c	3 Dec 2004 21:00:18 -0000	1.26
@@ -10,7 +10,7 @@
  *
  *  Kern Sibbald, July MMIII
  *
- *   Version $Id: 1.36.1-pool.patch 1866 2005-03-06 13:45:35Z kerns $
+ *   Version $Id: 1.36.1-pool.patch 1866 2005-03-06 13:45:35Z kerns $
  *
  *  This code was adapted from the Bacula workq, which was
  *    adapted from "Programming with POSIX Threads", by
@@ -40,6 +40,7 @@
 #include "bacula.h"
 #include "dird.h"
 
+extern JCR *jobs;
 
 /* Forward referenced functions */
 extern "C" void *jobq_server(void *arg);
@@ -47,6 +48,8 @@
 
 static int   start_server(jobq_t *jq);
 
+
+
 /*   
  * Initialize a job queue
  *
@@ -544,6 +547,7 @@
 	 for ( ; je;  ) {
 	    /* je is current job item on the queue, jn is the next one */
 	    JCR *jcr = je->jcr;
+	    bool skip_this_jcr = false;
 	    jobq_item_t *jn = (jobq_item_t *)jq->waiting_jobs->next(je);
             Dmsg3(300, "Examining Job=%d JobPri=%d want Pri=%d\n",
 	       jcr->JobId, jcr->JobPriority, Priority);
@@ -560,14 +564,40 @@
 		  jcr->store->MaxConcurrentJobs = 1;
 	       } else {
 		  set_jcr_job_status(jcr, JS_WaitStoreRes);
-		  je = jn;
+		  je = jn;	      /* point to next waiting job */
 		  continue;
 	       }
+	    /* We are not doing a Restore or Verify */
+	    } else if (jcr->store->NumConcurrentJobs == 0 &&
+		       jcr->store->NumConcurrentJobs < jcr->store->MaxConcurrentJobs) {
+		/* Simple case, first job */
+		jcr->store->NumConcurrentJobs = 1;  
 	    } else if (jcr->store->NumConcurrentJobs < jcr->store->MaxConcurrentJobs) {
-	       jcr->store->NumConcurrentJobs++;
-	    } else {
+	       /*
+		* At this point, we already have at least one Job running 
+		*  for this Storage daemon, so we must ensure that there
+		*  is no Volume conflict. In general, it should be OK, if
+		*  all Jobs pull from the same Pool, so we check the Pools.
+		*/
+		JCR *njcr;
+		lock_jcr_chain();
+		for (njcr=jobs; njcr; njcr=njcr->next) {
+		   if (njcr->JobId == 0 || njcr == jcr) {
+		      continue;
+		   }
+		   if (njcr->pool != jcr->pool) {
+		      skip_this_jcr = true;
+		      break;
+		   }
+		}  
+		unlock_jcr_chain();
+		if (!skip_this_jcr) {
+		   jcr->store->NumConcurrentJobs++;    
+		}
+	    } 
+	    if (skip_this_jcr) {
 	       set_jcr_job_status(jcr, JS_WaitStoreRes);
-	       je = jn;
+	       je = jn; 	      /* point to next waiting job */
 	       continue;
 	    }
 
@@ -580,7 +610,7 @@
 		  jcr->store->MaxConcurrentJobs = jcr->saveMaxConcurrentJobs;  
 	       }
 	       set_jcr_job_status(jcr, JS_WaitClientRes);
-	       je = jn;
+	       je = jn; 	      /* point to next waiting job */
 	       continue;
 	    }
 	    if (jcr->job->NumConcurrentJobs < jcr->job->MaxConcurrentJobs) {
@@ -593,7 +623,7 @@
 	       }
 	       jcr->client->NumConcurrentJobs--;
 	       set_jcr_job_status(jcr, JS_WaitJobRes);
-	       je = jn;
+	       je = jn; 	      /* Point to next waiting job */
 	       continue;
 	    }
 	    /* Got all locks, now remove it from wait queue and append it
@@ -603,7 +633,7 @@
 	    jq->waiting_jobs->remove(je);
 	    jq->ready_jobs->append(je);
             Dmsg1(300, "moved JobId=%d from wait to ready queue\n", je->jcr->JobId);
-	    je = jn;
+	    je = jn;		      /* Point to next waiting job */
 	 } /* end for loop */
 	 break;
       } /* end while loop */
Index: src/lib/jcr.c
===================================================================
RCS file: /cvsroot/bacula/bacula/src/lib/jcr.c,v
retrieving revision 1.61
retrieving revision 1.62
diff -u -r1.61 -r1.62
--- src/lib/jcr.c	15 Nov 2004 22:43:33 -0000	1.61
+++ src/lib/jcr.c	3 Dec 2004 21:00:19 -0000	1.62
@@ -3,7 +3,7 @@
  *
  *  Kern E. Sibbald, December 2000
  *
- *  Version $Id: 1.36.1-pool.patch 1866 2005-03-06 13:45:35Z kerns $
+ *  Version $Id: 1.36.1-pool.patch 1866 2005-03-06 13:45:35Z kerns $
  *
  *  These routines are thread safe.
  *
@@ -43,7 +43,7 @@
 dlist *last_jobs = NULL;
 const int max_last_jobs = 10;
 
-static JCR *jobs = NULL;	      /* pointer to JCR chain */
+JCR *jobs = NULL;		      /* pointer to JCR chain */
 static brwlock_t lock;		      /* lock for last jobs and JCR chain */
 
 void init_last_jobs_list()