<p>MySQL error 1811 (ER_IO_WRITE_ERROR) occurs when the server cannot write data to disk, often due to disk-space shortages, permission issues, or hardware faults.</p>
<p>MySQL Error 1811: ER_IO_WRITE_ERROR means the server failed to write a file to disk. Check free disk space, file-system permissions, and hardware health, then retry the write or relocate the data directory.</p>
IO Write error: (%lu, %s) %s
Error 1811 fires when the MySQL server or storage engine attempts to write a file and the underlying operating system returns an input-output write failure. The message usually appears as: IO Write error: (code, errno) path. It surfaces during data-modifying operations such as INSERT, UPDATE, or ALTER TABLE that need to flush pages or create temporary files.
Because MySQL cannot complete the disk write, the current transaction rolls back and the client receives SQLSTATE HY000. Leaving the issue unresolved risks data loss and prolonged downtime.
The error is most common on busy production servers running out of disk space or quota. It can also occur after file-system corruption, sudden power loss, or misconfigured permissions that prevent mysqld from creating or extending files.
Cloud environments trigger the same failure if attached block storage reaches capacity or is mounted read-only due to host-side faults.
Continued IO write errors stop new data from being persisted and may crash MySQL. If the binary log or redo log cannot be written, replication and recovery points become inconsistent, leading to potential data loss.
Rapid remediation restores write capability, keeps replication in sync, and avoids forced downtime, making this error a priority for database administrators.
Low free disk space is the leading cause. When InnoDB cannot extend ibdata files, redo logs, or temporary tablespaces, it raises ER_IO_WRITE_ERROR immediately.
Incorrect directory or file permissions deny mysqld write access, leading to the same failure even with ample disk space.
Hardware failures such as bad sectors or dying SSDs make the operating system reject write calls, surfacing as error 1811.
Read-only mounts, full disk quotas, and kernel-level IO throttling can also block writes unexpectedly.
First verify free disk space with df -h or the Windows equivalent. If usage is 100 percent, provision additional storage or purge old data, logs, and backups.
Next check permissions of datadir, tmpdir, and log directories. Ensure the MySQL service account owns them and has rw access.
Review system logs (dmesg, /var/log/messages) for drive errors. Replace faulty disks and run fsck to repair corrupted file systems.
If using cloud volumes, confirm the block device is writable and expand capacity as needed.
Binary log directory full: Move or purge old binlogs, update expire_logs_days, and restart replication.
Error during ALTER TABLE ... ALGORITHM=INPLACE: Increase tmpdir space or switch tmpdir to a larger partition.
InnoDB redo log cannot grow: Adjust innodb_log_file_size only after freeing disk space, then restart MySQL.
Implement continuous monitoring of disk usage with Prometheus, Nagios, or CloudWatch alarms set below 80 percent.
Separate data, log, and temporary directories onto different volumes to localize growth.
Automate log rotation and purging of binlogs, general logs, and slow logs.
Schedule regular filesystem integrity checks and keep firmware and drivers updated.
Error 1030 (HY000) Got error N from storage engine - generic storage engine IO error often preceding 1811.
Error 1812 (ER_IO_READ_ERROR) surfaces when reads, not writes, fail - diagnose with similar disk checks.
Error 1878 (Table is read only) appears when the filesystem is mounted read-only - remount rw to resolve.
Data, logs, or temporary files fill the partition, leaving no free blocks for MySQL to write.
mysqld lacks write rights on the data directory or tmp directory after migrations or manual chmod.
Bad sectors, controller errors, or corrupted ext4/NTFS files stop successful writes.
Operating system mounts the volume read-only after an error or user exceeds assigned quota.
Raised when read operations, not writes, fail on disk. Investigate with the same hardware and filesystem checks.
Generic storage engine error that can wrap underlying IO failures including error 1811.
Occurs when MySQL detects a read-only filesystem or tablespace. Remount the filesystem rw to resolve.
No. While low space is common, permissions, read-only mounts, and hardware faults can trigger the same write failure.
Even one IO write error signals an underlying issue that may escalate. Investigate immediately to protect data.
Yes. If the master cannot write the binary log, replicas fall behind. Clear the error, then restart replication threads.
Galaxy lets teams track disk-usage queries and share alerts, ensuring storage issues are caught before they break writes.
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