Understanding and Tuning Linux I/O Schedulers

By Admin · Feb 25, 2026 · Updated Apr 24, 2026 · 122 views · 2 min read

What Are I/O Schedulers?

The I/O scheduler determines the order in which read and write requests are sent to storage devices. The right scheduler can significantly impact performance depending on your workload and storage type.

Available Schedulers

Scheduler	Best For	Description
none/noop	NVMe SSDs	No reordering — passes requests directly to the device
mq-deadline	SSDs, databases	Guarantees request latency with deadlines
bfq	Desktop, interactive	Budget Fair Queueing — prioritizes interactive I/O
kyber	Fast SSDs	Low-overhead scheduler for high-IOPS devices

Check Current Scheduler

# Shows active scheduler in brackets
cat /sys/block/sda/queue/scheduler
# Example output: [mq-deadline] kyber bfq none

Change Scheduler Temporarily

echo "mq-deadline" | sudo tee /sys/block/sda/queue/scheduler

Change Scheduler Permanently

Create a udev rule at /etc/udev/rules.d/60-ioscheduler.rules:

# NVMe drives — use none
ACTION=="add|change", KERNEL=="nvme[0-9]*", ATTR{queue/scheduler}="none"

# SATA SSDs — use mq-deadline
ACTION=="add|change", KERNEL=="sd[a-z]", ATTR{queue/rotational}=="0", ATTR{queue/scheduler}="mq-deadline"

# HDDs — use bfq
ACTION=="add|change", KERNEL=="sd[a-z]", ATTR{queue/rotational}=="1", ATTR{queue/scheduler}="bfq"

Queue Depth Tuning

# Check current queue depth
cat /sys/block/sda/queue/nr_requests

# Increase for high-throughput workloads
echo 256 | sudo tee /sys/block/sda/queue/nr_requests

General Recommendations

NVMe: Use none — the device has its own scheduler
SSD: Use mq-deadline for databases, kyber for general workloads
HDD: Use bfq for mixed workloads