Redis has RDB persistence enabled but cannot write snapshots to disk, blocking write operations. This typically indicates disk space, permission, or memory issues preventing background saves.
This error occurs when Redis is configured with RDB (Snapshotted Database) persistence enabled, but fails to perform a background save operation (BGSAVE). When Redis cannot persist data to disk and has the 'stop-writes-on-bgsave-error' option enabled (the default), it blocks all write operations to prevent data loss. The underlying causes are usually disk-related (insufficient space, permission issues) or memory constraints that prevent Redis from forking child processes needed for background saves.
First, verify that your system has sufficient disk space for Redis snapshots:
df -h /var/lib/redisEnsure the filesystem where Redis data is stored has free space available. Redis needs space for the current RDB file plus temporary space for creating new snapshots. If disk space is below 10-20%, free up space before proceeding.
Check that the Redis process has proper permissions to read and write in its data directory:
sudo ls -ld /var/lib/redisThe directory should be owned by the redis user and group with 755 permissions:
sudo chown -R redis:redis /var/lib/redis
sudo chmod 755 /var/lib/redisEnsure the redis process can write snapshot files. Check the configured directory in redis.conf for the 'dir' setting.
Redis logs contain specific reasons for BGSAVE failures. Check the Redis log file:
sudo tail -f /var/log/redis/redis-server.logOr view recent errors:
sudo tail -n 100 /var/log/redis/redis-server.logLook for messages about fork failures, memory issues, or I/O errors. These will indicate the root cause (e.g., 'Cannot allocate memory').
On Linux systems, Redis requires memory overcommit enabled for background saves to work:
cat /proc/sys/vm/overcommit_memoryIf the output is 0, enable memory overcommit:
sudo sysctl vm.overcommit_memory=1To make this permanent, add to /etc/sysctl.conf:
echo "vm.overcommit_memory = 1" | sudo tee -a /etc/sysctl.conf
sudo sysctl -pThis allows Redis to fork child processes safely during background saves without the OS incorrectly predicting memory requirements.
After fixing the underlying issue, restart Redis:
Linux (systemd):
sudo systemctl restart redis-serverLinux (service):
sudo service redis restartmacOS:
brew services restart redisVerify Redis is running and check the status:
redis-cli pingIf Redis responds with 'PONG', the server is online.
Once Redis is restarted, verify that write operations work:
redis-cliInside redis-cli, test a SET command:
SET test-key "Hello World"
GET test-keyIf both commands succeed, the MISCONF error is resolved. You should see the value back when running GET.
The 'stop-writes-on-bgsave-error' configuration option (default: yes) is intentionally strict. When enabled, Redis stops accepting writes if RDB snapshots fail, forcing administrators to address persistence issues rather than silently losing data. Only disable this setting (CONFIG SET stop-writes-on-bgsave-error no) if you don't require data durability or don't have RDB snapshots enabled. For high-availability deployments, consider using AOF (Append-Only File) persistence instead, which doesn't require background forking. Docker containers often encounter this error due to low memory limits - ensure adequate memory allocation (at least 256MB for small instances, 1GB+ for production). The error may also occur after OS upgrades or kernel parameter changes that affect memory overcommit settings.
ERR Unbalanced XREAD list of streams
How to fix "ERR Unbalanced XREAD list" in Redis
ERR syntax error
How to fix "ERR syntax error" in Redis
ConnectionError: Error while reading from socket
ConnectionError: Error while reading from socket in redis-py
ERR unknown command
How to fix ERR unknown command in Redis
Command timed out
How to fix 'Command timed out' in ioredis