0. PrefaceIf the data is read/written from disk, the CPU is idle, wasting the compute power of this wait time CPU. So the SSD, cache, memory, register and so on is designed to reduce the CPU waiting time, the release of computing power. The industry's attention to disk I/O and the impact of disk I/O on the system can be seen.
I. How to view disk I/O
Under the Linux platform or BSD platform, disk I/O can be clearly seen with the top command.
two. How to measure disk I/O bottlenecksdisk I/O bottlenecks depend on the total number of cores of the current machine CPU (total number of cores calculation step to my other blog post: Linux performance monitoring----Load Average). Formula: X (IO) = 1/(Total CPU count) is used to measure disk I/O, the machine for example, this machine 2 CPU 12 core is the total number of cores is 2*12 = X (IO) = 0.04166666 = 4.17%. if the indicator is longer than 4.17%, our website response may be slower.
three. What are the factors that affect I/O performancemeasuring I/O performance a term called IOPS (input/output per-second) input or output per second
There are 4 factors that affect IOPS:-Multi-disk array (multidisk Arrays): The more disk IOPS in the array. If a disk has a IOPS, then 2 disk has a total ioPS-Average IOPS per disk (Average iops per-drive): Higher disk speeds, of course, higher IOPS-raid (see Https://en.wikipedia.org/wiki/RAID) Factor: Use RAID technology storage. RAID has a lot of performance costs when writing operations. For RAID6, 6 disk operations are required per write. RAID1 and RAID10 require 2 disk operations per write. -Read and writeWorkload: For example, in RAID 5 or RAID 6 There is a lot of write operations, IOPS will be very low
four. How to troubleshoot I/O bottleneckswe can tune the disk, which is complex and does not exceed the speed of RAM. So, the fastest way to handle an I/O-high service or application is to cache the data to RAM. For example, the database server's memory is configured to the highest, and SQL data is cached as much as possible.
Linux Performance Monitoring-disk I/O
