MySQL Error 27 EE_SYNC: Can't sync file to disk – Fix and Prevent

What is MySQL error code 27 (EE_SYNC)?<\/h2>

MySQL raises error 27 EE_SYNC with message "Can't sync file '%s' to disk (OS errno %d - %s)" when it calls fsync or fdatasync and the operating system returns a failure code. The server cannot guarantee that modified data has reached persistent storage, so it aborts the current statement and often marks the table as crashed.<\/p>

The problem sits between MySQL and the underlying file system.

Disk-full conditions, permission changes, network-attached storage glitches, or hardware errors all block the sync call. Ignoring the warning risks data loss and table corruption, so immediate investigation is essential.<\/p>

What Causes This Error?<\/h3>

Disk space exhaustion forces fsync to fail, triggering EE_SYNC.

Check both data and log partitions because binary logs and temp files grow quickly during heavy workloads.<\/p>

File-system corruption or read-only remounts stop write operations mid-transaction, making every subsequent sync call fail until the volume is repaired and remounted read-write.<\/p>

Storage hardware failures such as bad sectors or dead SSD cells surface through OS error codes 5 (EIO) or 30 (EROFS), which MySQL passes on in the EE_SYNC message.<\/p>

Incorrect permissions or SELinux/AppArmor policies can block MySQL from opening files with write+sync flags, especially after manual chmod or security policy changes.<\/p>

How to Fix MySQL Error 27 EE_SYNC<\/h3>

Start by reading the accompanying OS errno in the message.

Errno 28 means no space left on device, while Errno 30 indicates a read-only file system. Tail the MySQL error log and dmesg for disk-level messages to pinpoint the root cause.<\/p>

Free disk space or grow the partition if you see Errno 28. For Errno 30 or 5, unmount and run fsck, replace faulty drives, then remount the volume read-write.

Restart MySQL after the underlying storage is healthy.<\/p>

If the table was marked crashed, run CHECK TABLE and REPAIR TABLE, or restore from a recent backup if corruption persists.<\/p>

Common Scenarios and Solutions<\/h3>

Binary log flood - Rotate or purge old binary logs with PURGE BINARY LOGS TO 'mysql-bin.010000'; then enable binlog_expire_logs_seconds for automatic cleanup.<\/p>

Huge temp tables on disk - Increase tmp_table_size and monitor temp file paths; move tmpdir to a larger partition.<\/p>

Network file system hiccup - Ensure NFS mounts use sync, hard, and appropriate rsize/wsize options.

Failing NFS writes manifest as EE_SYNC until the mount stabilizes.<\/p>

Containerized deployments - Map persistent volumes with correct fsync support. Some overlay drivers ignore fsync, so switch to a driver that honors durability guarantees.<\/p>

Best Practices to Avoid This Error<\/h3>

Implement monitoring for disk usage, IOPS latency, and MySQL error codes.

Alert at 80 percent capacity to act before space exhaustion occurs.<\/p>

Separate data, log, and temporary files onto different volumes to prevent a single directory from filling up all space.<\/p>

Schedule regular fsck scans during maintenance windows and keep firmware on SSDs up to date to reduce unexpected I/O errors.<\/p>

Use MySQL innodb_flush_method=O_DIRECT or O_DSYNC where supported to control how data is flushed and lower the chance of OS errors under heavy load.<\/p>

Related Errors and Solutions<\/h3>

Error 28 - No space left on device: Free space or extend the file system.<\/p>

Error 1030 - Got error 28 from storage engine: Also indicates disk full; identical remediation steps.<\/p>

Error 1878 - Table is marked as crashed: Often appears after EE_SYNC; run REPAIR TABLE.<\/p>

Error 1290 - Read only mode: Triggered if file system remounts read-only; remount read-write and restart MySQL.<\/p>.