199 lines
4.0 KiB
Markdown
199 lines
4.0 KiB
Markdown
# Linux Disk Monitoring and Tuning
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## 1. Disk Monitoring Tools
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### iostat
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iostat provides detailed I/O statistics for devices and partitions. It shows CPU utilization and disk I/O statistics.
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Usage:
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```bash
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iostat [options] [interval] [count]
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```
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Key metrics:
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- %util: Percentage of CPU time during which I/O requests were issued
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- r/s and w/s: Read and write requests per second
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- rkB/s and wkB/s: Read and write kilobytes per second
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### iotop
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iotop is an interactive I/O monitoring tool that shows per-process I/O usage.
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Usage:
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```bash
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iotop
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```
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### dstat
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dstat is a versatile tool for generating system resource statistics.
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Usage:
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```bash
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dstat --disk --io --disk-util
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```
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### vmstat
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vmstat reports information about processes, memory, paging, block I/O, traps, and CPU activity.
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Usage:
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```bash
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vmstat [interval] [count]
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```
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### fdisk
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fdisk is a dialog-driven program for creation and manipulation of partition tables.
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Usage:
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```bash
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fdisk -l
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```
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## 2. Disk Performance Testing
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### dd
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dd can be used for simple disk read/write performance tests.
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Example (write test):
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```bash
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dd if=/dev/zero of=testfile bs=1G count=1 oflag=dsync
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```
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Example (read test):
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```bash
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dd if=testfile of=/dev/null bs=1G count=1
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```
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### fio
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fio is a flexible I/O tester for benchmark and stress/hardware verification.
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Example:
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```bash
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fio --name=random-write --ioengine=posixaio --rw=randwrite --bs=4k --size=4g --numjobs=1 --runtime=60 --time_based --end_fsync=1
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```
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## 3. File System Monitoring
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### df
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df reports file system disk space usage.
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Usage:
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```bash
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df -h
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```
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### du
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du estimates file and directory space usage.
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Usage:
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```bash
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du -sh /path/to/directory
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```
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## 4. Disk Tuning Techniques
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### I/O Scheduler
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Linux offers different I/O schedulers. Common ones include:
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- CFQ (Completely Fair Queuing)
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- Deadline
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- NOOP
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To check the current scheduler:
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```bash
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cat /sys/block/sda/queue/scheduler
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```
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To change the scheduler:
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```bash
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echo "deadline" > /sys/block/sda/queue/scheduler
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```
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### Read-ahead
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Adjust the read-ahead value to optimize for your workload:
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```bash
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blockdev --getra /dev/sda
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blockdev --setra 8192 /dev/sda
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```
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### Swappiness
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Reduce swappiness to minimize disk writes:
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```
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sysctl vm.swappiness=10
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```
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### Disk Cache
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Adjust the ratio of cached dirty memory:
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```bash
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sysctl -w vm.dirty_ratio=10
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sysctl -w vm.dirty_background_ratio=5
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```
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### TRIM (for SSDs)
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Enable TRIM for SSDs to maintain performance:
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```bash
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fstrim -v /
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```
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Or add the `discard` option to the mount options in /etc/fstab.
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### Journaling
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For ext4 file systems, you can disable journaling for better write performance (at the cost of data integrity):
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```bash
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tune2fs -O ^has_journal /dev/sda1
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```
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### Noatime
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Use the `noatime` mount option to reduce disk writes:
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In /etc/fstab:
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```ini
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UUID=xxx / ext4 defaults,noatime 0 1
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```
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## 5. Monitoring Tools for Long-term Analysis
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### sysstat
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sysstat includes tools like sar (System Activity Reporter) for long-term performance monitoring.
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To enable data collection:
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```bash
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systemctl enable sysstat
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systemctl start sysstat
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```
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To view collected data:
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```bash
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sar -d
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```
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### Prometheus + Node Exporter + Grafana
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For a more comprehensive monitoring solution:
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- Install and configure Prometheus
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- Set up Node Exporter on monitored systems
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- Create dashboards in Grafana for visualization
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## 6. Best Practices
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### Regular Maintenance
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- Run fsck regularly on unmounted file systems
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- Use SMART monitoring tools for early warning of disk failures
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- Perform regular backups
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### Capacity Planning
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- Monitor disk usage trends
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- Plan for capacity increases before running out of space
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### RAID Considerations
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- Use appropriate RAID levels for your use case
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- Monitor RAID health and replace failed disks promptly
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### SSD-specific Considerations
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- Enable TRIM
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- Monitor SSD wear levels
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- Consider over-provisioning for write-heavy workloads
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This guide covers the basics of Linux disk monitoring and tuning. Remember that optimal settings depend on your specific hardware and workload. Always test changes in a non-production environment first.
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