Most Linux admins are not aware of hidden switch (undocumented switch) called -D. The -D option display a nice summery of disk I/O subsystem since boot time. Output includes total time spent reading and writing data, merged reads and merged writes (kernel disk i/o optimization technique) and other parameters.
vmstat command with -D option
Type the command at shell prompt:
vmstat -D
Output:
30 disks
8 partitions
13739406 total reads
3887474 merged reads
1180260353 read sectors
109630647 milli reading
118650080 writes
250115464 merged writes
2950543038 written sectors
2382220771 milli writing
0 inprogress IO
113832 milli spent IOThis is my local backup server hosted at local data center:
$ uptime
Output:
12:15:07 up 33 days, 9:15, 2 users, load average: 1.71, 1.49, 1.03
Since last 33 days my server spent total 1180260353 milliseconds reading disk. To get more detailed about disk I/O stats, use the -d option as described in previous article - How do I find out Linux Disk utilization?
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