The Linux kernel's I/O scheduler is responsible for optimizing the order in which block I/O requests from the kernel's block layer are submitted to storage devices. This process, known as I/O scheduling, can have a significant impact on system performance.
There are three primary goals of I/O scheduling:
The I/O scheduler in the Linux kernel is designed to balance these three goals.
There are three I/O scheduling algorithms available in the Linux kernel:
The Deadline I/O scheduler is the default I/O scheduler in the Linux kernel. It is designed to minimize latency by giving priority to requests from processes with lower I/O priority.
The Noop I/O scheduler is a very simple I/O scheduler that does not reorder requests. It is typically used for devices with very low I/O latency, such as solid-state drives.
The CFQ I/O scheduler is the default I/O scheduler on most Linux distributions. It is designed to balance the three goals of I/O scheduling: minimizing seek time, merging requests, and reducing latency.
The I/O scheduler can be changed on a per-device basis using the -s
option of the blockdev
command. For example, to change the I/O scheduler of /dev/sda
to the Deadline I/O scheduler, you would use the following command:
blockdev -s /dev/sda deadline
The I/O scheduler can also be changed on a per-filesystem basis. To change the I/O scheduler of the /
filesystem to the CFQ I/O scheduler, you would use the following command:
mount -o remount,ioscheduler=cfq /
The I/O scheduler can have a significant impact on disk performance. For example, the Deadline I/O scheduler is designed to minimize latency by giving priority to requests from processes with lower I/O priority. This can result in increased performance for processes with high I/O priority, such as database servers.
The CFQ I/O scheduler is designed to balance the three goals of I/O scheduling: minimizing seek time, merging requests, and reducing latency. This can result in increased performance for most workloads.
The I/O scheduler in the Linux kernel is responsible for optimizing the order in which block I/O requests from the kernel's block layer are submitted to storage devices. There are three primary goals of I/O scheduling: improve performance by reordering requests to minimize seeks, improve performance by merging requests, and reduce latency by giving priority to requests from processes with lower I/O priority.
The I/O scheduler can have a significant impact on disk performance. The Deadline I/O scheduler is designed to minimize latency by giving priority to requests from processes with lower I/O priority. The CFQ I/O scheduler is designed to balance the three goals of I/O scheduling: minimizing seek time, merging requests, and reducing latency.