Fsync files – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 2-2

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Briefly, this error occurs when Elasticsearch is unable to synchronize its data files to the disk. This could be due to insufficient disk space, disk I/O issues, or file system permissions. To resolve this issue, you can try freeing up disk space, checking the disk for errors, or adjusting file system permissions. Additionally, ensure that the Elasticsearch process has the necessary permissions to write to the data directory. If the problem persists, consider moving the data directory to a different disk with more space or better performance.

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This guide will help you check for common problems that cause the log ” {} fsync files ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: bootstrap.

Log Context

Log “{} fsync files” classname is MultiDataPathUpgrader.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

        if (movedFiles.isEmpty() == false) {
            // fsync later it might be on disk already
            logger.info("{} fsync files"; shard);
            for (Path moved : movedFiles) {
                logger.info("{} syncing [{}]"; shard; moved.getFileName());
                IOUtils.fsync(moved; false);
            logger.info("{} syncing directory [{}]"; shard; targetDir);


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