Hi developers!
Thanks for your great work to develop DRBD.
I'm developing middleware at a Japanese company
and trying to incorporate DRBD into our project.
As a result of various tests, the following questions were raised.
Could you answer the following questions?
1. Can DRBD only provide up to 80 MB/s of network bandwidth per volume
during the initial full synchronization?
We did an initial full synchronization in DRBD with the following settings:
(I use a network with a speed of 1.25 GB/s.)
----
resource r0 {
disk {
c-plan-ahead 0;
rsync-rate 8388608;
}
net {
protocol C;
}
volume 0 {
device /dev/drbd1;
disk /dev/vg/lv01;
meta-disk internal;
}
volume 1 {
device /dev/drbd2;
disk /dev/vg/lv02;
meta-disk internal;
}
volume 2 {
device /dev/drbd3;
disk /dev/vg/lv03;
meta-disk internal;
}
volume 3 {
device /dev/drbd4;
disk /dev/vg/lv04;
meta-disk internal;
}
on host01 {
address 10.1.1.31:7789;
node-id 0;
}
on host02 {
address 10.1.1.32:7789;
node-id 1;
}
connection {
host host01 port 7012;
host host02 port 7021;
}
}
----
At this time, the overall sync speed was about 320 MB/s.
Then, I increased the number of volumes from the above settings to 8
and performed an initial full synchronization again,
and the sync speed was about 640 MB/s.
From these results, it seems that DRBD can only provide a sync speed of only 80
MB/s per volume.
(Strictly speaking, is DRBD reading 80MB/s per volume?)
2. Related to the previous question,
can DRBD provide a fast sync rate (For example, about 1.25 GB/s) for a one
volume?
In our project, we want to achieve fast synchronization speed with less volume.
For example, is it possible to achieve a sync rate of 1.25 GB/s with only 4
volumes?
3. Is the maximum number of peers in DRBD 32?
The drbdadm command with the following options completes successfully:
# drbdadm create-md --max-peers 32 r0
("--max-peers 33" results in an error.)
Defined in the drbd-utils source code as follows:
https://github.com/LINBIT/drbd-utils/blob/master/user/v84/linux/drbd.h
#define MAX_PEERS 32
However, resynchronization does not work well with the metadata created by the
above command.
Resynchronization works well with metadata created with "--max-peers" set to 31.
Is the maximum number of peers in DRBD really 32?
The DRBD version and the DRBD Utils version and OS version used are as follows:
DRBD: 9.0.16 (kmod-drbd90-9.0.16-1.el7_6.elrepo.x86_64.rpm)
DRBD Utils: 9.6.0 (drbd90-utils-9.6.0-1.el7.elrepo.x86_64.rpm)
OS: Red Hat Enterprise Linux 7.6
Thanks!
- tsubaki
.
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