[dm-devel] IO monitoring of dm devices with iostat

[Dmitry Ivanov]

	Hello!
Can you help me with iostat monitoring of /dev/dm-* and /dev/sd* 
devices.  Main question is about understanding of tps value. For example 
/dev/dm-5 is a dm-mapper-device based on /dev/sde and /dev/sdc.  tps 
value of dm-5 is 30% bigger than sde+sdf. According to stats from 
storage, right TPS io value is sde+sdf. Why /dev/dm* values differ while 
other columns are the same? How to treat this numbers?
	Thank you!

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
            0.16    0.00    0.08    0.02    0.00   99.73

Device:            tps    MB_read/s    MB_wrtn/s    MB_read    MB_wrtn
sda               0.50         0.00         0.01          0          0
sda1              0.00         0.00         0.00          0          0
sda2              0.50         0.00         0.01          0          0
sdb               0.00         0.00         0.00          0          0
sdb1              0.00         0.00         0.00          0          0
sdc               0.43         0.00         0.01          0          0
sdc1              0.00         0.00         0.00          0          0
sdc2              0.43         0.00         0.01          0          0
sdd               0.00         0.00         0.00          0          0
sdd1              0.00         0.00         0.00          0          0
sde              38.00         0.00         0.25          0          7
sde1             38.00         0.00         0.25          0          7
sdf              38.50         0.00         0.25          0          7
sdf1             38.50         0.00         0.25          0          7
dm-0              3.70         0.00         0.01          0          0
dm-1              0.00         0.00         0.00          0          0
dm-2              3.70         0.00         0.01          0          0
dm-3              3.70         0.00         0.01          0          0
dm-4              0.00         0.00         0.00          0          0
dm-5            126.43         0.00         0.49          0         14
dm-6            126.43         0.00         0.49          0         14
dm-7              0.00         0.00         0.00          0          0
dm-8              0.00         0.00         0.00          0          0



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