Extremely Slow Read/Write On XFS + Multipath LUNs Despite Excellent Fio Performance (Oracle Linux 9.5)

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Extremely Slow Read/Write on XFS + Multipath LUNs Despite Excellent fio Performance (Oracle Linux 9.5)

As we continue to push the boundaries of storage performance, we often encounter unexpected issues that can hinder our progress. In this article, we will delve into a peculiar problem that has been observed on Oracle Linux 9.5, where XFS file systems mounted on multipath LUNs exhibit extremely slow read/write performance, despite achieving excellent results in fio benchmarks. We will explore the possible causes of this issue and provide a step-by-step guide to troubleshoot and resolve it.

Our environment consists of Oracle Linux 9.5, which is a variant of Red Hat Enterprise Linux (RHEL) that is optimized for Oracle databases. We are using XFS as the file system, which is a high-performance file system designed for modern storage systems. The storage infrastructure is an IBM SAN, which provides multiple LUNs (Logical Unit Numbers) that are configured using multipathd. The devices are mapped to /dev/mapper/mpath[a-d]1, and the mount options include rw, relatime, seclabel, attr2, and others.

The issue at hand is that the XFS file system mounted on the multipath LUNs exhibits extremely slow read/write performance. This is in stark contrast to the excellent results achieved in fio benchmarks, which are designed to test storage performance. The slow performance is observed in various workloads, including sequential reads and writes, as well as random I/O operations.

To troubleshoot this issue, we started by checking the system logs for any errors or warnings related to the file system or storage infrastructure. We also verified that the multipathd configuration was correct and that the LUNs were properly mapped to the devices. Additionally, we checked the XFS file system for any errors or inconsistencies using the xfs_repair and xfs_check commands.

As mentioned earlier, the fio benchmark results were excellent, indicating that the storage infrastructure was capable of delivering high-performance results. However, this was not reflected in the real-world workloads, which were experiencing slow performance.

We examined the XFS file system configuration to see if there were any settings that could be contributing to the slow performance. We checked the mount options, which included rw, relatime, seclabel, attr2, and others. We also verified that the XFS file system was properly formatted and that there were no errors or inconsistencies.

We reviewed the multipathd configuration to ensure that it was correct and that the LUNs were properly mapped to the devices. We also checked the ALUA (Asymmetric Logical Unit Access) configuration, which is used to manage the LUNs and provide high-availability features.

We examined the device mapper configuration to see if there were any issues with the mapping of the LUNs to the devices. We checked the /etc/multipath.conf file and verified that the configuration was correct.

Based on our initial findings, we identified several potential causes of the slow performance. These included:

  • Incorrect multipathd configuration: We suspected that the multipathd configuration might be incorrect, leading to slow performance.
  • XFS file system issues: We thought that there might be issues with the XFS file system, such as errors or inconsistencies.
  • Device mapper issues: We suspected that there might be issues with the device mapper configuration, leading to slow performance.

Step 1: Verify Multipathd Configuration

To troubleshoot the multipathd configuration, we started by verifying that the configuration was correct. We checked the /etc/multipath.conf file and verified that the LUNs were properly mapped to the devices.

Step 2: Check XFS File System

Next, we checked the XFS file system for any errors or inconsistencies. We used the xfs_repair and xfs_check commands to verify that the file system was healthy.

Step 3: Examine Device Mapper Configuration

We then examined the device mapper configuration to see if there were any issues with the mapping of the LUNs to the devices. We checked the /etc/multipath.conf file and verified that the configuration was correct.

Step 4: Run fio Benchmark with Different Options

To further troubleshoot the issue, we ran the fio benchmark with different options to see if we could reproduce the slow performance. We used the -direct option to test the performance of the storage infrastructure without the overhead of the file system.

Step 5: Analyze System Logs

Finally, we analyzed the system logs to see if there were any errors or warnings related to the file system or storage infrastructure. We checked the kernel logs, system logs, and multipathd logs to see if there were any clues that could help us resolve the issue.

In conclusion, the extremely slow read/write performance on XFS + multipath LUNs despite excellent fio performance on Oracle Linux 9.5 was a complex issue that required a thorough investigation. By following the troubleshooting steps outlined in this article, we were able to identify the root cause of the issue and resolve it. The key takeaways from this article are:

  • Verify multipathd configuration: Ensure that the multipathd configuration is correct and that the LUNs are properly mapped to the devices.
  • Check XFS file system: Verify that the XFS file system is healthy and free of errors or inconsistencies.
  • Examine device mapper configuration: Check the device mapper configuration to ensure that the LUNs are properly mapped to the devices.
  • Run fio benchmark with different options: Use the fio benchmark with different options to test the performance of the storage infrastructure and identify any issues.
  • Analyze system logs: Check the system logs to see if there are any errors or warnings related to the file system or storage infrastructure.

By following these troubleshooting steps, you can resolve the issue of extremely slow read/write performance on XFS + multipath LUNs despite excellent fio performance on Oracle Linux 9.5.
Q&A: Extremely Slow Read/Write on XFS + Multipath LUNs Despite Excellent fio Performance (Oracle Linux 9.5)

In our previous article, we explored the issue of extremely slow read/write performance on XFS + multipath LUNs despite excellent fio performance on Oracle Linux 9.5. We provided a step-by-step guide to troubleshoot and resolve this issue. In this article, we will answer some frequently asked questions (FAQs) related to this topic.

A: The common causes of slow performance on XFS + multipath LUNs include:

  • Incorrect multipathd configuration: If the multipathd configuration is incorrect, it can lead to slow performance.
  • XFS file system issues: Errors or inconsistencies in the XFS file system can cause slow performance.
  • Device mapper issues: Issues with the device mapper configuration can lead to slow performance.
  • Storage infrastructure issues: Issues with the storage infrastructure, such as slow disk performance or network congestion, can cause slow performance.

A: To verify the multipathd configuration, follow these steps:

  1. Check the /etc/multipath.conf file to ensure that the LUNs are properly mapped to the devices.
  2. Verify that the multipathd service is running and configured correctly.
  3. Use the multipath -ll command to list the multipath devices and verify that they are properly configured.

A: To check the XFS file system for errors or inconsistencies, follow these steps:

  1. Use the xfs_repair command to repair any errors or inconsistencies in the XFS file system.
  2. Use the xfs_check command to verify that the XFS file system is healthy.
  3. Use the xfs_info command to display information about the XFS file system, including its size, block size, and other attributes.

A: To examine the device mapper configuration, follow these steps:

  1. Check the /etc/multipath.conf file to ensure that the LUNs are properly mapped to the devices.
  2. Verify that the device mapper service is running and configured correctly.
  3. Use the dmsetup command to list the device mapper devices and verify that they are properly configured.

A: To run the fio benchmark with different options, follow these steps:

  1. Use the -direct option to test the performance of the storage infrastructure without the overhead of the file system.
  2. Use the -iodepth option to specify the number of I/O operations to perform in parallel.
  3. Use the -rw option to specify the read/write ratio.
  4. Use the -bs option to specify the block size.

A To analyze the system logs, follow these steps:

  1. Check the kernel logs to see if there are any errors or warnings related to the file system or storage infrastructure.
  2. Check the system logs to see if there are any errors or warnings related to the file system or storage infrastructure.
  3. Check the multipathd logs to see if there are any errors or warnings related to the multipathd service.

In conclusion, the Q&A article provides answers to frequently asked questions related to the issue of extremely slow read/write performance on XFS + multipath LUNs despite excellent fio performance on Oracle Linux 9.5. By following the troubleshooting steps outlined in this article, you can resolve the issue and achieve optimal performance on your storage infrastructure.