nodetool listsnapshots

Displays a list of all snapshots on the node with their sizes.

---

Synopsis

nodetool [connection_options] listsnapshots [options]

See connection options for connection options.

Description

nodetool listsnapshots shows all snapshots on the local node, including:

• Snapshot tag name
• Keyspace and table names
• True data size
• Disk space consumed

Essential for monitoring backup state and managing disk space.

---

Options

Option	Description
-e, --ephemeral	Include ephemeral snapshots
-k, --keyspace <keyspace>	Filter by keyspace name
-n, --snapshot <name>	Filter by snapshot name
-nt, --no-ttl	Exclude snapshots with TTL
-t, --table <table>	Filter by table name

---

Output Example

Snapshot Details:
Snapshot name       Keyspace name      Column family name   True size   Size on disk   Creation time
backup_20240115     my_keyspace        users                1.5 GB      1.5 GB         2024-01-15T10:30:00Z
backup_20240115     my_keyspace        orders               2.3 GB      2.3 GB         2024-01-15T10:30:00Z
backup_20240108     my_keyspace        users                1.2 GB      0 bytes        2024-01-08T10:30:00Z
backup_20240108     my_keyspace        orders               2.1 GB      0 bytes        2024-01-08T10:30:00Z
pre_upgrade         system_schema      tables               45 MB       45 MB          2024-01-14T22:00:00Z

Total TrueDiskSpaceUsed: 7.15 GB

---

Output Fields

Field	Description
Snapshot name	Tag used when creating the snapshot
Keyspace name	Keyspace containing the table
Column family name	Table name
True size	Actual data size in the snapshot
Size on disk	Current disk space consumed
Creation time	When the snapshot was created

Understanding Size Fields

True size	Size on disk	Meaning
1.5 GB	1.5 GB	Original SSTables still exist (hard links)
1.5 GB	0 bytes	Original SSTables compacted away (space freed)
1.5 GB	500 MB	Partially compacted

Size on Disk

"Size on disk" shows actual disk blocks consumed. When original SSTables are compacted, the hard links become the only reference, and size on disk increases.

---

Examples

List All Snapshots

nodetool listsnapshots

Include Ephemeral Snapshots

nodetool listsnapshots -e

Exclude TTL Snapshots

nodetool listsnapshots -n

Filter by Snapshot Name

nodetool listsnapshots | grep backup_20240115

Total Snapshot Size

nodetool listsnapshots | tail -1

Count Snapshots

nodetool listsnapshots | grep -c "^[a-zA-Z]"

---

When to Use

Before Creating New Snapshots

Check existing snapshots to avoid duplicates:

nodetool listsnapshots | grep my_new_tag

Disk Space Investigation

When disk usage is high:

nodetool listsnapshots
# Check Total TrueDiskSpaceUsed at the bottom

Backup Verification

Verify snapshot was created:

nodetool snapshot -t my_backup my_keyspace
nodetool listsnapshots | grep my_backup

Cleanup Planning

Identify snapshots to remove:

nodetool listsnapshots
# Find old snapshots by creation time

---

Interpreting Results

Recently Created Snapshot

backup_20240115     my_keyspace     users     1.5 GB     1.5 GB     2024-01-15T10:30:00Z

• True size = Size on disk = Original SSTables still exist
• Hard links share disk blocks with active SSTables
• Minimal additional space used

Aged Snapshot

backup_20240101     my_keyspace     users     1.5 GB     1.5 GB     2024-01-01T10:30:00Z

After compaction runs:

• Original SSTables removed
• Snapshot files become sole reference
• Now consuming full 1.5 GB

No Snapshots

Snapshot Details:

Total TrueDiskSpaceUsed: 0 bytes

No snapshots exist on this node.

---

Monitoring Snapshot Growth

Check All Nodes

for node in node1 node2 node3; do
    echo "=== $node ==="
    ssh "$node" "nodetool listsnapshots | tail -3"
done

Track Over Time

# Log snapshot sizes daily
echo "$(date),$(nodetool listsnapshots | tail -1 | awk '{print $2}')" >> /var/log/snapshot_sizes.csv

Alert on Large Snapshots

total=$(nodetool listsnapshots | tail -1 | awk '{print $2}' | sed 's/GB//')
if (( $(echo "$total > 100" | bc -l) )); then
    echo "WARNING: Snapshot usage exceeds 100GB"
fi

---

Snapshot Location on Disk

Snapshots are stored in:

/var/lib/cassandra/data/<keyspace>/<table>-<uuid>/snapshots/<tag>/

To manually check sizes:

# All snapshots
du -sh /var/lib/cassandra/data/*/*/snapshots/*

# Specific snapshot
du -sh /var/lib/cassandra/data/*/*/snapshots/backup_20240115/

---

Common Issues

Empty Output

If no snapshots are shown but you expect them:

1. Check if snapshots were taken on this node
2. Verify snapshot directory exists:

   ls /var/lib/cassandra/data/*/*/snapshots/

Incorrect Size Reported

Size reporting depends on filesystem support for hard links:

• Some filesystems may not accurately report shared blocks
• Use du for precise measurements if needed

Very Large Total Size

Old snapshots consuming significant space:

# Identify largest snapshots
nodetool listsnapshots | sort -k4 -h

# Clear old snapshots
nodetool clearsnapshot -t old_snapshot_tag

---

Best Practices

Snapshot Monitoring Guidelines

1. Regular checks - Include in daily monitoring
2. Set retention alerts - Alert when snapshots age
3. Track total size - Monitor growth trends
4. Clean up promptly - Remove snapshots after backup verification
5. Use TTL snapshots - Auto-delete when possible (4.0+)
6. Document naming - Use consistent, dated snapshot names

---

Related Commands

Command	Relationship
snapshot	Create snapshots
clearsnapshot	Remove snapshots
tablestats	Table-level statistics