I use veeam 8.0 U3 on ESXi 5.5 (build 3116895) and I have getting a lot more snapshot consolidation errors than normal during backups and replication. it happens after the backup job is complete, but the helper snapshot is being removed.
here is a piece of my logs. why would it only need 4 MB of space, but still fail to consolidate? I would think my storage system would have enough performance capacity to consolidate 4 MB!
2016-04-02T03:49:58.774Z| vcpu-0| I120: DISKLIB-CBT : Initializing ESX kernel change tracking for fid 529995229.
2016-04-02T03:49:58.775Z| vcpu-0| I120: DISKLIB-CBT : Successfuly created cbt node 1e4715de-cbt.
2016-04-02T03:49:58.775Z| vcpu-0| I120: DISKLIB-CBT : Opening cbt node /vmfs/devices/cbt/1e4715de-cbt
2016-04-02T03:49:58.775Z| vcpu-0| I120: DISKLIB-LIB : Opened "/vmfs/volumes/56f2dac6-dce63fdf-cb74-24b6fdf42ea2/serverNEW/serverNEW-000001.vmdk" (flags 0x18, type vmfsSparse).
2016-04-02T03:49:58.779Z| vcpu-0| I120: DISKLIB-CBT : Shutting down change tracking for untracked fid 529995229.
2016-04-02T03:49:58.779Z| vcpu-0| I120: DISKLIB-CBT : Successfully disconnected CBT node.
2016-04-02T03:49:58.782Z| vcpu-0| I120: DISKLIB-CBT : Shutting down change tracking for untracked fid 614667738.
2016-04-02T03:49:58.783Z| vcpu-0| I120: DISKLIB-CBT : Successfully disconnected CBT node.
2016-04-02T03:49:58.812Z| vcpu-0| I120: DISKLIB-CHAINESX : ChainESXOpenSubChain: numLinks = 2, numSubChains = 1
2016-04-02T03:49:58.812Z| vcpu-0| I120: DISKLIB-CHAINESX : ChainESXOpenSubChain:(0) fid = 614667738, extentType = 2
2016-04-02T03:49:58.812Z| vcpu-0| I120: DISKLIB-CHAINESX : ChainESXOpenSubChain:(1) fid = 529995229, extentType = 0
2016-04-02T03:49:58.813Z| vcpu-0| I120: DISKLIB-CBT : Initializing ESX kernel change tracking for fid 529995229.
2016-04-02T03:49:58.813Z| vcpu-0| I120: DISKLIB-CBT : Successfuly created cbt node 1e4915de-cbt.
2016-04-02T03:49:58.813Z| vcpu-0| I120: DISKLIB-CBT : Opening cbt node /vmfs/devices/cbt/1e4915de-cbt
2016-04-02T03:49:58.956Z| vcpu-0| I120: DISKLIB-LIB : Free disk space is less than imprecise space neeeded for combine (0x2efff000 < 0x87e8f000, in sectors). Getting precise space needed for combine...
2016-04-02T03:50:10.512Z| vcpu-0| I120: DISKLIB-LIB : Upward Combine 2 links at 0. Need 4 MB of free space (385022 MB available)
2016-04-02T03:50:10.535Z| vcpu-0| I120: DDB: "longContentID" = "6af8a6ef5c498e3a7db7897fc8d9df95" (was "12958a23e31e7f680028e70eff8cf0ee")
2016-04-02T03:50:20.675Z| vcpu-0| I120: SnapshotVMXConsolidateHelperProgress: Stunned for 21 secs (max = 12 secs). Aborting consolidate.
2016-04-02T03:50:20.675Z| vcpu-0| I120: DISKLIB-VMFS_SPARSE : Cancelling vmfs combine.
2016-04-02T03:50:20.675Z| vcpu-0| I120: DISKLIB-CTK : End Combine
2016-04-02T03:50:20.677Z| vcpu-0| I120: DISKLIB-CTK : Attempting unlink of (null)
2016-04-02T03:50:20.677Z| vcpu-0| I120: SNAPSHOT: SnapshotCombineDisks: Failed to combine: Operation was canceled (33).
2016-04-02T03:50:20.680Z| vcpu-0| I120: DISKLIB-CBT : Shutting down change tracking for untracked fid 529995229.
2016-04-02T03:50:20.681Z| vcpu-0| I120: DISKLIB-CBT : Successfully disconnected CBT node.
2016-04-02T03:50:20.707Z| vcpu-0| I120: DISKLIB-VMFS : "/vmfs/volumes/56f2dac6-dce63fdf-cb74-24b6fdf42ea2/serverNEW/serverNEW-000001-delta.vmdk" : closed.
2016-04-02T03:50:20.709Z| vcpu-0| I120: DISKLIB-VMFS : "/vmfs/volumes/56f2dac6-dce63fdf-cb74-24b6fdf42ea2/serverNEW/serverNEW-flat.vmdk" : closed.
2016-04-02T03:50:20.710Z| vcpu-0| I120: SNAPSHOT: Snapshot_ConsolidateWorkItem failed: Operation was canceled (5)
2016-04-02T03:50:20.710Z| vcpu-0| I120: SnapshotVMXConsolidateOnlineCB: Synchronous consolidate failed for disk node: scsi0:8. Adding it to skip list.
2016-04-02T03:50:20.740Z| vcpu-0| I120: SnapshotVMXConsolidateOnlineCB: nextState = 1 uid 0
2016-04-02T03:50:20.740Z| vcpu-0| I120: SnapshotConsolidateWorkItemArrayGet: Skipping node scsi0:8.
2016-04-02T03:50:20.740Z| vcpu-0| I120: Closing all the disks of the VM.
2016-04-02T03:50:20.740Z| vcpu-0| I120: SnapshotVMXConsolidateOnlineCB: Branching work item.
2016-04-02T03:50:20.799Z| vcpu-0| I120: DISKLIB-VMFS : "/vmfs/volumes/56febc22-6d95c2cb-8947-24b6fdf42ea2/serverNEW/serverNEW-000002-delta.vmdk" : open successful (29) size = 17702912, hd = 0. Type 8
2016-04-02T03:50:20.800Z| vcpu-0| I120: DISKLIB-LIB : Resuming change tracking.