Applications are running slower than normal
Impact : Medium
High levels of disk I/O may result in slow disk response times. This may create a bottleneck, degrading the user experience, resulting in poor efficiency of your organization’s operations. A long-term consequence of over-activity in disk hardware may be a reduction in hardware life, or even catastrophic disk crashes in real-time.
Expected behavior :
There is no standard metric for disk utilization level. An alert means your threshold has been passed. Based on our experience, disk utilization should be less than 70%. As well as this metric, other AimBetter metrics such as Page Life Expectancy, Disk available space, Disk read/Disk write response and Memory free % should all be reviewed to get a full picture of the cause of any bottlenecks.
Redesign program to maximize use of indexed data. Redesign table structures to match the requirements of the programs by building indexes. Make use of temporary tables.
The faulty hardware component should be replaced immediately.
If the program calls for output to the disk ( I/O ) and the disk is nearly full (generally the optimal threshold is below 90% of total capacity), the disk will start to slow down as it searches for free space. This will cause the program to wait for progressively longer periods.
Examine the disk free-space reporting from AimBetter Dashboard > Resources > Disk. If necessary, working with operating system reports, identify whether there is sufficient space in unnecessary files (for example, old or redundant copies of data), to delete these files and run a disk clean-up. If there is still not enough, further disk capacity must be added.)
When the program calls for rapid disk reads – typically when searching and analyzing random data, disk utiliztion will increase rapidly..
Possible actions :
- Redesign program to maximize use of indexed data
- Redesign table structures to match the requirements of the programs by building indexes
- Make use of temporary tables
Missing indexes will cause extensive data searching from disk, resulting in page swapping.
See our explanation for missing/corrupt indexes here.
This alerts means that the hard disk is too busy, therefore cannot apply the input/output operations at the pace that the programs demand. Since demand for disk activity may be coming both from the operating system and SQL, use AimBetter QAnalyzer to identify any queries that are performing high levels of physical I/O or CPU usage.
Disk I/O overload can also manifest itself as exceptionally high CPU load. A task waiting for disc IO will be taken off the CPU until it has been answered by the scheduler. What this means is that the CPU is 100% busy but in power saving mode because of all the waiting while longer query queues are forming. This will slow all CPU-dependent processes, resulting in overall degradation in server performance.
Microsoft SQL Server uses Microsoft Windows operating system input/output (I/O) calls to perform read and write operations on your disk. SQL Server manages when and how disk I/O is performed, but the Windows operating system performs the underlying I/O operations. The I/O subsystem includes the system bus, disk controller cards, disks, tape drives, CD-ROM drive, and many other I/O devices. Disk I/O is frequently the cause of bottlenecks in a system.