[DRBD-user] umount /drbdpart takes >50 seconds

[Harald Dunkel]

Hi folks,

using drbd umounting /data1 takes >50 seconds, even though the file
system (ext4, noatime, default) wasn't accessed for more than 2h.
umount ran with 100% CPU load.

# sync
# time umount /data1

real    0m52.772s
user    0m0.000s
sys     0m52.740s


This appears to be a pretty long time. I am concerned that there
is some data sleeping in a buffer that gets flushed only at umount
time.

Kernel is version 4.18.0-0.bpo.1-amd64 on Debian Stretch. drbdutils
is 8.9.10-2. drbd.conf is attached. The bond2 interface used for
drbd synchronization is based upon 2 * 10 Gbit/sec NICs.


Every insightful comment is highly appreciated.

Regards
Harri

#
# see http://www.drbd.org/users-guide-8.4/re-drbdconf.html
# https://www.linbit.com/en/drbd-sync-rate-controller-2/
#
# /etc/hosts
# ~~~~~~~~~~~
# br0 ("external" network interface)
# 192.168.96.184        srvl060a.example.com srvl060a
# 192.168.96.185        srvl060b.example.com srvl060b
#
# bond2 ("internal" network interface, used for drbd synchronization)
# 10.0.0.2      srvl060a.internal
# 10.0.0.3      srvl060b.internal
#
common {
        disk {
                # on-io-error   detach;                 # continue in diskless 
mode (default)
                fencing resource-only;                  # use fence-peer 
handler 
                resync-rate     512M;                   # synchronization rate 
over a dedicated line (4 each disk!)
                c-plan-ahead    0;
                al-extents 1237;                        # activity log extents
        }

        net {
                protocol C;
                max-buffers     32k;
                max-epoch-size  20000;
                sndbuf-size     256k;
                rcvbuf-size     512k;
                # allow-two-primaries;
                cram-hmac-alg sha256;
                # generated using "openssl rand -base64 30":
                shared-secret "YTbwx3QGiBf2xDrWN+9VppvsrOTXFKRy67x3FAu0";
                after-sb-0pri disconnect;
                after-sb-1pri disconnect;
                after-sb-2pri disconnect;
                rr-conflict disconnect;
        }

        startup {
                wfc-timeout 300;
                degr-wfc-timeout 30;
                outdated-wfc-timeout 30;
        }

        handlers {
                pri-on-incon-degr "echo o > /proc/sysrq-trigger ; halt -f";
                pri-lost-after-sb "echo o > /proc/sysrq-trigger ; halt -f";
                fence-peer "/usr/lib/drbd/outdate-peer.sh on 
srvl060a.example.com 192.168.96.185 10.0.0.3 on srvl060b.example.com 
192.168.96.184 10.0.0.2";
                local-io-error "echo o > /proc/sysrq-trigger ; halt -f";

                initial-split-brain "/usr/lib/drbd/notify-split-brain.sh";
                split-brain "/usr/lib/drbd/notify-split-brain.sh";
        }
}

resource data1 {
        device          /dev/drbd1;
        disk            /dev/disk/by-partlabel/data1;
        meta-disk       internal;
        on srvl060a.example.com {
                address         10.0.0.2:7788;
        }
        on srvl060b.example.com {
                address         10.0.0.3:7788;
        }
        startup {
                become-primary-on srvl060a.example.com;
        }
}

resource data2 {
        device          /dev/drbd2;
        disk            /dev/disk/by-partlabel/data2;
        meta-disk       internal;
        on srvl060a.example.com {
                address         10.0.0.2:7789;
        }
        on srvl060b.example.com {
                address         10.0.0.3:7789;
        }
        startup {
                become-primary-on srvl060b.example.com;
        }
}

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