Hi ,
i have a question regarding to the iostat output:
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s rkB/s wkB/s
avgrq-sz avgqu-sz await svctm %util
sdp 86432.30 0.00 3915.20 2.00 124267.20 2.00 62133.60
1.00 31.72 32.86 8.39 0.26 100.00
According to this output:
rrqm/s : 86432.3 , r/s:3915.2 , rkB/s : 62133.60 .
rrqm/s
The number of read requests merged per sec-
ond that were issued to the device.
The operating system merges multiple io requests into one read call ,
since these io requests are small from the basic io unit.
I have 86432.3 merge per second , with 3915.2 read per second. This
shows that , for 1 read operation , my system does 22 merge
.(86432.3/3915.2) . On the other hand , 62133.60 / 3915.2 = 15kb ,
each read operation issues 15Kb. from the underlying disk subsystem.
15kb/22 merge = 0,6 kb more or less 512b. So each io request in fact is
512byte , but since the minimum io that os can request is 15kb, they
are merged till the 15kb. size is reached.
Are these comments meaningful?
Kind Regards,
tolga
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