[DRBD-user] CPU Util for DRBD resources

Lars Ellenberg lars.ellenberg at linbit.com
Fri Nov 4 10:32:32 CET 2016

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


On Tue, Nov 01, 2016 at 07:02:02AM +0000, pillai bs wrote:
> Hi Experts,
> 
> 
> Is there a possible way to monitor CPU Util for the drbd resource.
> Actually am getting cent percent utilization even i dont have much
> load.
> 
> Am maintaining my setup with three blocks one for Data, other for
> configurations and the other for logs which was logically mounted.

DRBD version?
The stats you present below look like the "queue length" is
misaccounted.  Our iostats had some problems in the past, potentially
producing such bogus results.


Also, even when correct, %util may not be what you think it is.

%100 util does not mean it cannot take any more.
It only means that "most of the time" a new request is submitted before
previous requests have been completed, or maybe "back to back" with the
completion.

Depending on usage patterns, and network and IO backend latencies,
100% util may even be expected.

> [root at pcpha-dev-01 ~]# iostat -x 5  | grep drbd
> drbd0             0.00     0.00    0.00    0.00     0.00     0.00     0.00 858980.47    0.00   0.00  99.94
> drbd1             0.00     0.00    0.00    0.00     0.00     0.00     0.00   101.94    0.00   0.00  99.94
> drbd2             0.00     0.00    0.00    0.80     0.00     3.20     4.00 858935.49    0.25 1249.25  99.94
> drbd0             0.00     0.00    0.00    0.00     0.00     0.00     0.00 858980.46    0.00   0.00 100.00
> drbd1             0.00     0.00    0.00    0.00     0.00     0.00     0.00   102.00    0.00   0.00 100.00
> drbd2             0.00     0.00    0.00    2.80     0.00    19.20     6.86 858935.46    0.07 357.14 100.00
> 
> [xxxx at xxxx]# iostat -x -d
> Linux 2.6.32-431.el6.x86_64 (xxxx)      10/31/2016      _x86_64_        (4 CPU)
> 
> Device:         rrqm/s   wrqm/s     r/s     w/s   rsec/s   wsec/s avgrq-sz             avgqu-sz   await  svctm  %util
> sda               0.00                  0.86    0.01    1.67    10.96    20.22    18.50                    0.00        0.73       0.41        0.07
> dm-0              0.00                0.00    0.00    0.02     0.05     0.12     9.97                      0.00         9.66       1.99        0.00
> dm-1              0.00               0.00    0.00    0.00     0.00     0.00     8.00                       0.00        2.14        0.82        0.00
> dm-2              0.00               0.00    0.00    0.02     0.02     0.12     9.22                       0.00         1.97        0.01        0.00
> dm-3              0.00               0.00    0.00    0.78     0.00     6.23     8.00                        0.00         0.48        0.21       0.02
> dm-4              0.00               0.00    0.00    0.00     0.00     0.00     7.99                        0.00         3.30      2.89        0.00
> dm-5              0.00                0.00    0.00    0.48     0.01     3.85     8.01                       0.00         0.64      0.22        0.01
> dm-6              0.00                0.00    0.00    0.01     0.00     0.04     8.00                      0.00        24.47     0.02         0.00
> dm-7              0.00               0.00    0.01    0.03     6.50     0.21   205.25                     0.00         37.54   1.13         0.00
> dm-8              0.00               0.00    0.00    0.02     2.21     0.15   109.64                    0.00          9.22      0.89        0.00
> dm-9              0.00                0.00    0.00    1.19     2.17     9.50     9.81                      0.00          0.65      0.31        0.04
> drbd0             0.00                 0.00    0.00    0.01     0.00     0.08     8.00                      0.20        421.71 10481.54  10.45
> drbd1             0.00                0.00    0.00    0.01     0.00     0.07     7.95                      0.06         76.94    12030.16  10.49
> drbd2             0.00                 0.00    0.00    0.56     0.00     3.26     5.85                      0.15         0.61      176.92   9.87
> 
> [xxxx at xxxx]# iostat -x 5 /dev/vg1/lvdblog
> Linux 2.6.32-431.el6.x86_64 (xxxx)      10/31/2016      _x86_64_        (4 CPU)
> 
> 
> avg-cpu:  %user   %nice %system %iowait  %steal   %idle
>            2.21    0.00    0.75    0.00    0.00   97.04
> 
> Device:         rrqm/s   wrqm/s     r/s     w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
> dm-9              0.00     0.00    0.00    1.60     0.00    12.80     8.00     0.00    1.00   0.62   0.10


-- 
: Lars Ellenberg
: LINBIT | Keeping the Digital World Running
: DRBD -- Heartbeat -- Corosync -- Pacemaker

DRBD® and LINBIT® are registered trademarks of LINBIT
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