nodetool enablebackup

Enables incremental backup.

Synopsis

nodetool [connection_options] enablebackup

See connection options for connection options.

Description

nodetool enablebackup enables incremental backup mode. When enabled, Cassandra creates hard links to newly flushed SSTables in a backups subdirectory. This allows continuous backup of data as it's written.

Non-Persistent Setting

This setting is applied at runtime only and does not persist across node restarts. After a restart, incremental backup reverts to the incremental_backups setting in cassandra.yaml (default: false).

To make the change permanent, update cassandra.yaml:

incremental_backups: true

How Incremental Backup Works

When incremental backup is enabled:

Each time new SSTables are created (during flush, compaction, or other operations), a hard link is created
Hard links go to: <data_dir>/<keyspace>/<table>/backups/
Links point to the same data blocks (no extra disk space initially)
Backup files remain even after compaction removes the original

Example

nodetool enablebackup

Verify:

nodetool statusbackup
# Expected: running

Backup Location

/var/lib/cassandra/data/<keyspace>/<table>-<uuid>/backups/

Example:

/var/lib/cassandra/data/my_keyspace/my_table-abc123/backups/
├── nb-1-big-Data.db
├── nb-1-big-Index.db
├── nb-1-big-Filter.db
└── ...

Use Cases

Continuous Backup Strategy

# 1. Enable incremental backup
nodetool enablebackup

# 2. Periodically copy backup files to external storage
rsync -av /var/lib/cassandra/data/*/*/backups/ /backup/incremental/

# 3. Clear processed backups
rm -rf /var/lib/cassandra/data/*/*/backups/*

Combined with Snapshots

# Weekly full backup (snapshot)
nodetool snapshot -t weekly_$(date +%Y%m%d)

# Daily incremental backup
nodetool enablebackup
# ... copy backups daily ...

Incremental vs Snapshot Backup

Aspect	Incremental	Snapshot
Trigger	Automatic on flush	Manual command
Content	New SSTables only	All current SSTables
Disk usage	Grows over time	Point-in-time
Recovery	Need base + incrementals	Self-contained
Overhead	Continuous	On-demand

Workflow: Incremental Backup

# 1. Take initial snapshot (baseline)
nodetool snapshot -t baseline

# 2. Enable incremental backup
nodetool enablebackup

# 3. Application writes data...

# 4. Periodically copy incrementals
rsync -av /var/lib/cassandra/data/*/*/backups/ /backup/server/

# 5. Clear processed incrementals
find /var/lib/cassandra/data -path "*/backups/*" -delete

# 6. Repeat steps 4-5

Restoration Process

To restore from incremental backups:

# 1. Restore baseline snapshot
cp -r /backup/snapshots/baseline/* /var/lib/cassandra/data/

# 2. Layer incremental backups
cp -r /backup/incremental/* /var/lib/cassandra/data/

# 3. Start Cassandra or refresh
nodetool refresh keyspace table

Disk Space Considerations

Space Growth

Incremental backups consume disk space:

Hard links share data initially
After compaction, backup files use real space
Old backup files not automatically deleted

Monitoring Space

# Check backup directory size
du -sh /var/lib/cassandra/data/*/*/backups/

# Total backup size
find /var/lib/cassandra/data -path "*/backups/*" -type f -exec du -ch {} + | tail -1

Cleanup

# Remove processed backups
find /var/lib/cassandra/data -path "*/backups/*" -delete

Configuration

cassandra.yaml Setting

incremental_backups: true  # Or use nodetool enablebackup

Runtime vs Configuration

Method	Persistence
`nodetool enablebackup`	Until restart
`cassandra.yaml`	Permanent

Automation Script

#!/bin/bash
# incremental_backup.sh - Copy and clear incrementals

BACKUP_DIR="/backup/cassandra/incremental/$(date +%Y%m%d_%H%M)"
DATA_DIR="/var/lib/cassandra/data"

# Create backup directory
mkdir -p "$BACKUP_DIR"

# Copy incremental backups
for backup_path in $(find $DATA_DIR -type d -name "backups"); do
    if [ "$(ls -A $backup_path 2>/dev/null)" ]; then
        # Get relative path for organization
        rel_path=$(echo $backup_path | sed "s|$DATA_DIR/||")
        mkdir -p "$BACKUP_DIR/$rel_path"
        mv "$backup_path"/* "$BACKUP_DIR/$rel_path/"
    fi
done

echo "Incremental backup completed: $BACKUP_DIR"

Best Practices

Incremental Backup Guidelines

Start with a snapshot - Need baseline for recovery
Regular cleanup - Move and delete processed backups
Monitor disk space - Backups grow continuously
Test restoration - Verify backup/restore process
Document retention - Know what's backed up and when

Command	Relationship
disablebackup	Disable incremental backup
statusbackup	Check backup status
snapshot	Create full backup
listsnapshots	List snapshots