Hi, Chris!
If you have a RAID 0 on 3 disks, why does /dev/sdc on Primary server
stay inactive or so ? Isn't there kind of ugly thing happening on your
primary infrastructure ?
Then, your iostat results show different units, blocks on primary,
KBytes on secondary. The fact that you see different TPS values doesn't
mean much if the size of I/Os differs on both side. I'm no DRBD expert,
but are we sure that an X-sized IO on primary generates an identical IO
size on the secondary ? Might be that IOs are split into smaller units
on secondary... In that case, what we need is to compare apples with
apples : What are the KB values on primary ? I would suspect that they
are approximately the same. If not, then yes you might have something
odd happening. But I would rather expect similar values, in which case
it woud solely be a matter of differing IO size on both sides of the mirror.
Best regards,
Pascal.
Le 08/06/2011 02:06, Gouveia, Chris a écrit :
I have a two machine DRBD setup, supposedly with identical hardware in
both machines. I have 3 drives in each, with software RAID-0, and DRBD
on the RAID partition. When I write large amounts of data via NFS to the
DRBD partition, the harddrive LED on the primary machine blinks slowly.
However, on the secondary machine, the LED is on solidly. I also ran
iostat on the drives:
Primary machine
avg-cpu: %user %nice %system %iowait %steal %idle
0.25 0.00 4.93 25.52 0.00 69.30
Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sda 349.00 34960.00 680.00 34960 680
sdb 330.00 35112.00 544.00 35112 544
sdc 6.00 0.00 144.00 0 144
md0 2517.00 105736.00 1920.00 105736 1920
Secondary machine
avg-cpu: %user %nice %system %iowait %steal %idle
0.00 0.00 2.51 0.00 0.00 97.49
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 937.00 0.00 16316.00 0 16316
sdb 986.00 0.00 16248.00 0 16248
sdc 905.00 0.00 16324.00 0 16324
md0 12116.00 0.00 48464.00 0 48464
Notice that the secondary machine TPS is much higher than the primary
machine.
The two machines have identical configurations:
resource hnlcsv {
protocol B;
handlers {
pri-on-incon-degr
"/usr/lib/drbd/notify-pri-on-incon-degr.sh;
/usr/lib/drbd/notify-emergency-reboot.sh; echo b> /proc/sysrq-trigger ;
reboot -f";
pri-lost-after-sb
"/usr/lib/drbd/notify-pri-lost-after-sb.sh;
/usr/lib/drbd/notify-emergency-reboot.sh; echo b> /proc/sysrq-trigger ;
reboot -f";
local-io-error "/usr/lib/drbd/notify-io-error.sh;
/usr/lib/drbd/notify-emergency-shutdown.sh; echo o> /proc/sysrq-trigger
; halt -f";
}
net {
max-epoch-size 16000;
max-buffers 16000;
sndbuf-size 0;
}
disk {
use-bmbv;
}
syncer {
al-extents 3389;
rate 50M;
}
on hnlcsv4 {
device /dev/drbd0;
disk /dev/md0;
address 192.168.1.2:7789;
flexible-meta-disk internal;
}
on hnlcsv3 {
device /dev/drbd0;
disk /dev/md0;
address 192.168.1.1:7789;
flexible-meta-disk internal;
}
}
Does anyone know what could cause the secondary to work so hard? I think
if it didn't have to, I could get much higher throughput on my DRBD
partition because it's being limited by the secondary machine.
Thanks,
Chris Gouveia
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