Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Mon, Apr 30, 2012 at 11:32:01AM +0200, Matthieu Lejeune wrote:
> Hello,
>
> I'd like to know what is the real disk utilisation by the command "iostat"
>
> My drbd config :
>
> resource ssd {
> protocol C;
>
> startup {
> wfc-timeout 0;
> }
>
> disk {
> on-io-error detach;
> }
>
> syncer {
> rate 2000M;
> verify-alg md5;
> }
>
> on surtax {
> device /dev/drbd1;
> disk /dev/sdb;
> address 10.1.42.11:7789;
> meta-disk internal;
> }
>
> on relax {
> device /dev/drbd1;
> disk /dev/sdb;
> address 10.1.42.12:7789;
> meta-disk internal;
> }
> }
>
> When I launc Iostat with the physical Raid Disk sdb i have this :
>
> root at relax:~# iostat -x 1 /dev/sdb
> Linux 2.6.32-5-amd64 (relax) 04/30/2012 _x86_64_ (16 CPU)
>
> avg-cpu: %user %nice %system %iowait %steal %idle
> 0.00 0.00 0.86 0.02 0.00 99.12
>
> Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s
> avgrq-sz avgqu-sz await svctm %util
> sdb 204.38 139.59 861.77 164.35 27215.10 7050.02
> 33.39 0.74 0.72 0.24 24.96
>
> avg-cpu: %user %nice %system %iowait %steal %idle
> 0.00 0.00 1.83 0.00 0.00 98.17
>
> Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s
> avgrq-sz avgqu-sz await svctm %util
> sdb 187.00 1701.00 599.00 1676.00 26440.00 122096.00
> 65.29 0.98 0.43 0.22 50.80
>
>
> But when I launch de command with de drbd disk :
>
> root at relax:~# iostat -x 1 /dev/drbd1
> Linux 2.6.32-5-amd64 (relax) 04/30/2012 _x86_64_ (16 CPU)
>
> avg-cpu: %user %nice %system %iowait %steal %idle
> 0.00 0.00 0.86 0.02 0.00 99.12
>
> Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s
> avgrq-sz avgqu-sz await svctm %util
> drbd1 0.00 0.00 1066.49 272.73 27215.65 7019.34
> 25.56 1.26 1.61 0.75 99.99
>
> avg-cpu: %user %nice %system %iowait %steal %idle
> 0.00 0.00 2.82 0.00 0.00 97.18
>
> Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s
> avgrq-sz avgqu-sz await svctm %util
> drbd1 0.00 0.00 7533.00 191.00 254904.00 5910.00
> 33.77 7.49 0.82 0.13 100.00
>
>
> I don't know if my drive is 100% full or no ?
No it is not.
Besides iostat "utilization" not being useful at all for "virtual" disks
like DRBD, or MD or ... -- which is why md does not even provide
those statistics -- the statistics update in DRBD lacked a rounding
call, and thus was off on a wide range of kernels.
See:
http://git.drbd.org/gitweb.cgi?p=drbd-8.3.git;a=commitdiff;h=80cb2183911626747d3f7546fe3cb3c1abe6ba41
--
: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com
DRBD® and LINBIT® are registered trademarks of LINBIT, Austria.
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