[Tip] For disk IO subsystem total statistics

[Tha.Suresh]

vmstat - For disk IO subsystem total statistics since last boot use
the -D option

              $ vmstat -D
                 27 disks
                  2 partitions
            2766536 total reads
             526906 merged reads
           61184034 read sectors
           21233780 milli reading
            8849711 writes
            3719803 merged writes
          100480938 written sectors
          181253052 milli writing
                  0 inprogress IO
              12854 milli spent IO

    The last stat shows 12854 ms spent reading from the disk.

    Merged reads and merged writes happen when the kernel tries to
    combine requests for contiguous regions on the disk for a performance
    increase.

    If you want more detailed totals, use the -d option.

    An important note, vmstat can provide totals on disk performance whereas
    iostat provides data rate of change during the sample.

--
Warm Regards,
Tha.Suresh

My experiences with Linux:  http://thasulinux.wordpress.com
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[Ritesh Raj Sarraf]

On 07/13/2011 04:27 PM, Tha.Suresh wrote:
> vmstat - For disk IO subsystem total statistics since last boot use
> the -D option
>
> $ vmstat -D
> 27 disks
> 2 partitions

Anyone got an idea what it means when it says 27 disks ? I ran it on my
laptop and it said 12 disks. I have only one.

--
Ritesh Raj Sarraf
RESEARCHUT - http://www.researchut.com
"Necessity is the mother of invention."

[Ritesh Raj Sarraf]

On 07/14/2011 12:44 AM, Ritesh Raj Sarraf wrote:

Anyone got an idea what it means when it says 27 disks ? I ran it on my
laptop and it said 12 disks. I have only one.

Okay!!

access("/sys/block/sda", F_OK)          = 0
access("/sys/block/sda1", F_OK)         = -1 ENOENT (No such file or directory)
access("/sys/block/sda2", F_OK)         = -1 ENOENT (No such file or directory)
access("/sys/block/sda3", F_OK)         = -1 ENOENT (No such file or directory)
access("/sys/block/sr0", F_OK)          = 0
access("/sys/block/dm-0", F_OK)         = 0
access("/sys/block/dm-1", F_OK)         = 0
access("/sys/block/loop0", F_OK)        = 0
access("/sys/block/loop1", F_OK)        = 0
access("/sys/block/loop2", F_OK)        = 0
access("/sys/block/loop3", F_OK)        = 0
access("/sys/block/loop4", F_OK)        = 0
access("/sys/block/loop5", F_OK)        = 0
access("/sys/block/loop6", F_OK)        = 0
access("/sys/block/loop7", F_OK)        = 0

Total 15 block type files. -3 which are not block devices (partitions of the block dev).