[ClusterLabs] DRBD Dual Primary Write Speed Extremely Slow

[Tyler Phillippe]

Hello all,

I have setup a Linux cluster on 2x CentOS 8 Stream machines - it has resources to manage a dual primary, GFS2 DRBD setup. DRBD and the cluster have a diskless witness. Everything works fine - I have the dual primary DRBD working and it is able to present an iSCSI LUN out to my LAN. However, the DRBD write speed is terrible. The backing DRBD disks (HDD) are RAID10 using mdadm and they (re)sync at around 150MB/s. DRBD verify has been limited to 100MB/s, but left untethered, it will get to around 140MB/s. If I write data to the iSCSI LUN, I only get about 10-15MB/s. Here's the DRBD global_common.conf - these are exactly the same on both machines:

global {
        usage-count no;
        udev-always-use-vnr;
}

common {
        handlers {
        }

        startup {
                wfc-timeout 5;
                degr-wfc-timeout 5;
        }

        options {
                auto-promote yes;
                quorum 1;
                on-no-data-accessible suspend-io;
                on-no-quorum suspend-io;
        }

        disk {
                al-extents 4096;
                al-updates yes;
                no-disk-barrier;
                disk-flushes;
                on-io-error detach;
                c-plan-ahead 0;
                resync-rate 100M;
        }

        net {
                protocol C;
                allow-two-primaries yes;
                cram-hmac-alg "sha256";
                csums-alg "sha256";
                verify-alg "sha256";
                shared-secret "secret123";
                max-buffers 36864;
                rcvbuf-size 5242880;
                sndbuf-size 5242880;
        }
}

Respectfully,
 Tyler
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