# Sluggishness in DRBD resync in Rocky Linux 9.8 (worked on Rocky Linux 9.7) **URL:** \ **Category:** General\ **Tags:** drbd\ **Created:** [June 18, 2026, 1:44pm UTC](https://forums.linbit.com/t/sluggishness-in-drbd-resync-in-rocky-linux-9-8-worked-on-rocky-linux-9-7/1229 "2026-06-18T13:44:32Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Sharada](https://avatars.discourse-cdn.com/v4/letter/s/ba8739/32.png) [@Sharada](https://forums.linbit.com/u/Sharada)\ **Post date:** [June 18, 2026, 1:44pm UTC](https://forums.linbit.com/t/sluggishness-in-drbd-resync-in-rocky-linux-9-8-worked-on-rocky-linux-9-7/1229/1 "2026-06-18T13:44:32Z")
We are using DRBD to setup a high-availability environment. - **Kernel:** **Rocky Linux 9.8** → 5.14.0-687.10.1.el9\_8.0.1.x86\_64 - **DRBD version:** kmod-drbd9x-9.3.2-2.el9\_8& drbd9x-utils-9.34.0-1.el9 in Rocky 9.8. - **Symptom:** untuned dynamic resync is very slow around 250k c-min-rate floor (~0.30 MB/s) _ **drbdsetup status --verbose --statistics r0** _ _r0 node-id:1 role:Primary suspended:no force-io-failures:no_ ``` *write-ordering:flush* ``` _volume:0 minor:0 disk:UpToDate backing\_dev:/dev/vgpcp/lvbprhome quorum:yes_ ``` *open:yes* *size:20970844 read:11558042 written:133969 al-writes:0 bm-writes:7125 upper-pending:0 lower-pending:1* *al-suspended:no blocked:no* ``` _rocky98-xxx node-id:0 connection:Connected role:Secondary tls:no congested:no ap-in-flight:0_ ``` *rs-in-flight:0* *volume:0 replication:SyncSource peer-disk:Inconsistent done:55.42 resync-suspended:no* *received:425 sent:11557952 out-of-sync:9349224 pending:0 unacked:1 **dbdt1:0.30** eta:30778* ``` Earlier when we tested with Rocky Linux 9.7, we got the desired results; the untuned dynamic resync ramped to ~27 MB/s. DRBD version used in Rocky Linux 9.7 - kmod-drbd9x-9.3.0-1.el9\_7 & drbd9x-utils-9.33.0-1.el9. _ **drbdsetup status --verbose --statistics r0** _ _r0 node-id:1 role:Primary suspended:no force-io-failures:no_ _write-ordering:flus h_ _volume:0 minor:0 disk:UpToDate backing\_dev:/dev/vgpcp/lvbprhome quorum:y es_ _open: yes_ _size:20970844 read:6972490 written:133969 al-writes:5 bm-writes:341 upper-pending:0 lower-pendi ng:1_ _al-suspended:no block ed:no_ _rocky97-xxx node-id:0 connection:Connected role:Secondary tls:no congested:no ap-in-fl ight:0_ _rs-in-flig ht:6144_ _volume:0 replication:SyncSource peer-disk:Inconsistent done:33.54 resync-susp ended:no_ _received:425 sent:6972400 out-of-sync:13937848 pending:3 unacked:1 **dbdt1:27.5** 1 eta:495_ In both the Rocky Linux 9.8 and 9.7, we are having identical config & defaults. Same backing device, mq-deadline scheduler on both, vmxnet3 10G identical, **iperf3 ~32 Gbit/s with ~0 retransmits**. _disk {_ _resync-rate 250k; # bytes/second, default_ _c-plan-ahead 20; # 1/10 seconds, default_ _c-delay-target 10; # 1/10 seconds, default_ _c-fill-target 100s; # bytes, default_ _c-max-rate 102400k; # bytes/ second, default_ _c-min-rate 250k; # bytes /second, default_ _bitm ap yes; # default_ _resync-without-replication yes; #__default_ _}_ Why are we seeing very slow resync in Rocky 9.8? ---
**Author:** ![Devin](https://yyz1.discourse-cdn.com/flex003/user_avatar/forums.linbit.com/devin/32/26_2.png) [@Devin](https://forums.linbit.com/u/Devin)\ **Post date:** [June 18, 2026, 8:53pm UTC](https://forums.linbit.com/t/sluggishness-in-drbd-resync-in-rocky-linux-9-8-worked-on-rocky-linux-9-7/1229/2 "2026-06-18T20:53:01Z")
My guess is likely just the tuning. The defaults are a tad conservative because that is what is safe in most environments. Try tuning things a bit. I have a whole KB article on this exact topic here: [Tuning the DRBD Resync Controller | Knowledge Base](https://kb.linbit.com/drbd/tuning-the-drbd-resync-controller/) ---
**Author:** ![Sharada](https://avatars.discourse-cdn.com/v4/letter/s/ba8739/32.png) [@Sharada](https://forums.linbit.com/u/Sharada)\ **Post date:** [June 19, 2026, 8:24am UTC](https://forums.linbit.com/t/sluggishness-in-drbd-resync-in-rocky-linux-9-8-worked-on-rocky-linux-9-7/1229/3 "2026-06-19T08:24:57Z")
Hi Devin, Thank you for the response and the tuning suggestions. Before applying them, I’d like to understand the root cause. These defaults have worked well across Linux 6.x, 7.x, 8.x, and up to 9.7 — ramping to ~27 MB/s on the same hardware. Only after the upgrade to Rocky 9.8 — with identical config and identical DRBD defaults — does the controller now stay pinned around ~0.30 MB/s. The fact that 9.8 requires special tuning is bothering and hence this issue is reported to understand what changed so drastically in 9.8 to cause this. ---
**Author:** ![Sharada](https://avatars.discourse-cdn.com/v4/letter/s/ba8739/32.png) [@Sharada](https://forums.linbit.com/u/Sharada)\ **Post date:** [June 25, 2026, 2:41am UTC](https://forums.linbit.com/t/sluggishness-in-drbd-resync-in-rocky-linux-9-8-worked-on-rocky-linux-9-7/1229/4 "2026-06-25T02:41:26Z")
Hi Devin, Any insights on this? Thanks again! ---
**Author:** ![kermat](https://yyz1.discourse-cdn.com/flex003/user_avatar/forums.linbit.com/kermat/32/21_2.png) [@kermat](https://forums.linbit.com/u/kermat)\ **Post date:** [July 20, 2026, 4:18pm UTC](https://forums.linbit.com/t/sluggishness-in-drbd-resync-in-rocky-linux-9-8-worked-on-rocky-linux-9-7/1229/5 "2026-07-20T16:18:14Z")
Not totally sure, but I did search up this commit that sounds like it could be related: > > > drbd\_rs\_c\_min\_rate\_throttle() computed the recent resync rate as > db = rs\_mark\_le…ft\[i\] - rs\_left in unsigned long. When out-of-sync grows > (a SyncSource taking writes faster than it can resync), the subtraction > wraps to ~2\*\*64, dbdt dwarfs c-min-rate, and the resync is throttled > exactly when it is already starved -- worsening convergence. > > Compute db signed; if it is not shrinking (db \<= 0) the resync is below > any minimum rate, so do not throttle it. > > Signed-off-by: Lars Ellenberg \ > Signed-off-by: Philipp Reisner \ I’m not sure if that was recently broken and then fixed, but worth pointing out that something similar in nature was addressed in DRBD 9.3.3.