Address review comments from Gemini and CodeRabbit

Fix HIGH issues:
- Fix empty disk discovery: Now discovers all disks from VolumeInfos,
  not just from EC shards. This ensures disks without EC shards are
  still considered for placement.
- Fix EC shard count calculation in detection.go: Now correctly filters
  by DiskId and sums actual shard counts using ShardBits.ShardIdCount()
  instead of just counting EcShardInfo entries.

Fix MEDIUM issues:
- Add disk ID to evacuation log messages for consistency with other logging
- Remove unused serverToDisks variable in placement.go
- Fix comment that incorrectly said 'ascending' when sorting is 'descending'

weed/shell/command_ec_common.go

@@ -436,13 +436,29 @@ func collectEcVolumeServersByDc(topo *master_pb.TopologyInfo, selectedDataCenter
 			disks:      make(map[uint32]*EcDisk),
 		}
 
-		// Build disk-level information from EC shard info
+		// Build disk-level information from volumes and EC shards
+		// First, discover all unique disk IDs from VolumeInfos (includes empty disks)
+		allDiskIds := make(map[uint32]string) // diskId -> diskType
 		for diskType, diskInfo := range dn.DiskInfos {
 			if diskInfo == nil {
 				continue
 			}
+			// Get all disk IDs from volumes
+			for _, vi := range diskInfo.VolumeInfos {
+				allDiskIds[vi.DiskId] = diskType
+			}
+			// Also get disk IDs from EC shards
+			for _, ecShardInfo := range diskInfo.EcShardInfos {
+				allDiskIds[ecShardInfo.DiskId] = diskType
+			}
+		}
+
 		// Group EC shards by disk_id
 		diskShards := make(map[uint32]map[needle.VolumeId]erasure_coding.ShardBits)
+		for _, diskInfo := range dn.DiskInfos {
+			if diskInfo == nil {
+				continue
+			}
 			for _, ecShardInfo := range diskInfo.EcShardInfos {
 				diskId := ecShardInfo.DiskId
 				if diskShards[diskId] == nil {
@@ -451,24 +467,24 @@ func collectEcVolumeServersByDc(topo *master_pb.TopologyInfo, selectedDataCenter
 				vid := needle.VolumeId(ecShardInfo.Id)
 				diskShards[diskId][vid] = erasure_coding.ShardBits(ecShardInfo.EcIndexBits)
 			}
+		}
 
-			// If no EC shards, still create disk entry based on DiskInfo.DiskId
-			if len(diskShards) == 0 && diskInfo.DiskId > 0 {
-				diskShards[diskInfo.DiskId] = make(map[needle.VolumeId]erasure_coding.ShardBits)
+		// Create EcDisk for each discovered disk
+		diskCount := len(allDiskIds)
+		if diskCount == 0 {
+			diskCount = 1
 		}
+		freePerDisk := int(freeEcSlots) / diskCount
 
-			// Create EcDisk for each disk_id found
-			for diskId, shards := range diskShards {
+		for diskId, diskType := range allDiskIds {
+			shards := diskShards[diskId]
+			if shards == nil {
+				shards = make(map[needle.VolumeId]erasure_coding.ShardBits)
+			}
 			totalShardCount := 0
 			for _, shardBits := range shards {
 				totalShardCount += shardBits.ShardIdCount()
 			}
-				// Estimate free slots per disk (simplified: divide evenly if multiple disks)
-				diskCount := len(diskShards)
-				if diskCount == 0 {
-					diskCount = 1
-				}
-				freePerDisk := int(freeEcSlots) / diskCount
 
 			ecNode.disks[diskId] = &EcDisk{
 				diskId:       diskId,
@@ -478,7 +494,6 @@ func collectEcVolumeServersByDc(topo *master_pb.TopologyInfo, selectedDataCenter
 				ecShards:     shards,
 			}
 		}
-		}
 
 		ecNodes = append(ecNodes, ecNode)
 		totalFreeEcSlots += freeEcSlots

weed/shell/command_volume_server_evacuate.go

@@ -199,7 +199,11 @@ func (c *commandVolumeServerEvacuate) moveAwayOneEcVolume(commandEnv *CommandEnv
 			}
 			vid := needle.VolumeId(ecShardInfo.Id)
 			destDiskId := pickBestDiskOnNode(emptyNode, vid)
+			if destDiskId > 0 {
+				fmt.Fprintf(os.Stdout, "moving ec volume %s%d.%d %s => %s (disk %d)\n", collectionPrefix, ecShardInfo.Id, shardId, thisNode.info.Id, emptyNode.info.Id, destDiskId)
+			} else {
 				fmt.Fprintf(os.Stdout, "moving ec volume %s%d.%d %s => %s\n", collectionPrefix, ecShardInfo.Id, shardId, thisNode.info.Id, emptyNode.info.Id)
+			}
 			err = moveMountedShardToEcNode(commandEnv, thisNode, ecShardInfo.Collection, vid, shardId, emptyNode, destDiskId, applyChange)
 			if err != nil {
 				return

weed/storage/erasure_coding/placement/placement.go

@@ -114,8 +114,6 @@ func SelectDestinations(disks []*DiskCandidate, config PlacementRequest) (*Place
 
 	// Build indexes for efficient lookup
 	rackToDisks := groupDisksByRack(suitable)
-	serverToDisks := groupDisksByServer(suitable)
-	_ = serverToDisks // Used for reference
 
 	result := &PlacementResult{
 		SelectedDisks:   make([]*DiskCandidate, 0, config.ShardsNeeded),
@@ -130,7 +128,7 @@ func SelectDestinations(disks []*DiskCandidate, config PlacementRequest) (*Place
 
 	// Pass 1: Select one disk from each rack (maximize rack diversity)
 	if config.PreferDifferentRacks {
-		// Sort racks by number of available servers (ascending) to prioritize underutilized racks
+		// Sort racks by number of available servers (descending) to prioritize racks with more options
 		sortedRacks := sortRacksByServerCount(rackToDisks)
 		for _, rackKey := range sortedRacks {
 			if len(result.SelectedDisks) >= config.ShardsNeeded {

weed/worker/tasks/erasure_coding/detection.go

@@ -477,10 +477,15 @@ func diskInfosToCandidates(disks []*topology.DiskInfo) []*placement.DiskCandidat
 			freeSlots = 0
 		}
 
-		// Calculate EC shard count from EcShardInfos slice
+		// Calculate EC shard count for this specific disk
+		// EcShardInfos contains all shards, so we need to filter by DiskId and sum actual shard counts
 		ecShardCount := 0
 		if disk.DiskInfo.EcShardInfos != nil {
-			ecShardCount = len(disk.DiskInfo.EcShardInfos)
+			for _, shardInfo := range disk.DiskInfo.EcShardInfos {
+				if shardInfo.DiskId == disk.DiskID {
+					ecShardCount += erasure_coding.ShardBits(shardInfo.EcIndexBits).ShardIdCount()
+				}
+			}
 		}
 
 		candidates = append(candidates, &placement.DiskCandidate{