Slow write speeds DRBD


New Member
Sep 22, 2023
Hi all,

Since the github of drbd seems a bit dead i hope someone here can help us out since we're working with qemu and drbd:

Currently we are running 2 servers with a drbd configuration:
The machine we're logged into in this picture is the v02, where drbd1 is primary.

Here we run a Windows 2022 server with the following startup rules:
(originally we use aio=native,

Our harddisk is a WD nvme drive.
Ofcourse we want to see the high read/write numbers that this drive offers.
We did a lot of benchmarks with various flags disabled and enabled as mentioned above.
We also switched from 'virtio-blk' as device to 'nmve' which resulted in lower performance.

The problem:
When the drbd is synced and connected the benchmark results look like this:

When we give the command 'drbdadm disconnect drbd0' and 'drbdadm disconnect drbd1' the benchmark results look like this:

We already adjusted the /etc/drbd.conf:

  • changing protocol version,
  • changing maxbuffer & maxepoch
  • setting c-plan-ahead to 0
  • adjusting resyncrate
  • adjusting rate

Unfortunately nothing changed the result of the low write speeds when drbd is connected and in sync.

What could be the bottleneck why the writespeed is capped at ~115MB/s when the drbd is functioning normally?
i thought of that too, but why? because the server is running on the primary side locally. It shouldn't have to be dependant on the secondary side. the syncing can take place asynchronously right?


The Proxmox community has been around for many years and offers help and support for Proxmox VE, Proxmox Backup Server, and Proxmox Mail Gateway.
We think our community is one of the best thanks to people like you!

Get your subscription!

The Proxmox team works very hard to make sure you are running the best software and getting stable updates and security enhancements, as well as quick enterprise support. Tens of thousands of happy customers have a Proxmox subscription. Get yours easily in our online shop.

Buy now!