Hi there,
I had a split-brain situation and tried to resync both machines (running
Citrix Xenserver 5.6/ CentOS). But I figured out that the sync speed was
below normal - I remember sync rates between 100 and 250 MB/s. After a
few attempts I decided to have both machines reboot. But no improvement.
The current sync speed is around 5 kB/s.
I tried downloading a file to both machines which happened with > 500 KB/s.
Then I did a benchmark of the throughput between both machines with
"netio". The results are always > 200 MB/s.
As I said: Nothing has changed on the machines. Only the 10GbE switch
got four additional Mini GBICs and needed to be switched off for a few
minutes - this is when I wanted to turn one primary to secondary but
recognized that they where out of sync already.
Another thing worth to mention: When running the sync my virtual guests
on the Xenserver respond slowly. When executing "top" in dom0 CPU usage
seldomly reaches values higher than 3%.
Playing around with other syncer rates did not lead to an improvement.
MTU size is 9000. I played around with a few network "tweak" settings
when configuring the machines and had good results before. These values
have been stored in a script that I manually run at system start before
invoking DRBD.
Did anyone possibly have a similar problem already and could you suggest
where I could tweak the system to run the way it ran before?
DRBD is version 8.3.8.1 . Currently the sync is paused.
My "drbd.conf":
-------------------------------------------------------------
global { usage-count no; }
common {
protocol C;
net {
allow-two-primaries;
shared-secret "drbd";
after-sb-0pri discard-zero-changes;
after-sb-1pri consensus;
after-sb-2pri disconnect;
sndbuf-size 0;
no-tcp-cork;
unplug-watermark 8000;
max-buffers 8000;
max-epoch-size 8000;
}
disk {
max-bio-bvecs 1;
no-disk-flushes;
#no-md-flushes;
no-disk-barrier;
}
startup {
become-primary-on both;
}
handlers {
split-brain "/usr/lib/drbd/notify-split-brain.sh";
}
syncer {
al-extents 511;
rate 2048M;
}
}
resource drbd-sr1 {
device /dev/drbd0;
meta-disk internal;
on server1 {
address 192.168.30.201:7788 ;
disk /dev/disk/by-id/scsi-SAdaptec_data_84A1F62C ;
}
on server2 {
address 192.168.30.202:7788 ;
disk /dev/disk/by-id/scsi-SAdaptec_data_2548D82A ;
}
}
-------------------------------------------------------------
CU,
Mészi.
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