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From: Philipp Reisner <philipp.reisner@linbit.com>
To: drbd-announce@lists.linux.dev
Subject: drbd-9.2.21-rc.1 and drbd-9.3.5-rc.1
Date: Tue, 03 Nov 2026 19:41:25 +0100
Message-ID: <86a4npu59m.fsf@linbit.com>
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Hi,

The DRBD-9.3.5-rc.1 release brings two new features. First, it adds an
interface to use one of DRBD=E2=80=99s change-tracking bitmaps to support b=
ackup
software. Together with the new drbd-utils release, it adds new commands
to enable, reset, and dump tracked changes in an extent-list
format. This is compatible with what many backup software programs can
consume to optimize taking incremental backups. To get this to backup
software, LINSTOR will also support it, and our integrations with
Kubernetes, OpenStack, OpenNebula, and Apache CloudStack (and others if
possible) will support passing the CBT information as well.

The second new feature worth mentioning is a reworked RDMA transport. It
is called rdma2, and it builds on recent work (released with drbd-9.3.1)
allocating receive buffers in large chunks. Under optimal conditions,
that means with large BIOs, I saw lab machines maxing out a 100Gbps link
using Connext-X5 cards while replicating a write stream with DRBD.

Another change is completely transparent for you as users. We are
switching the netlink family to drbd2. This is an important step for
bringing drbd-9 to upstream Linux. It will allow us to have a drbd-9 in
upstream Linux that is compatible with very old drbd-8.4 drbd-utils.

On top of that, the release includes a large number of bug fixes. We
fixed many bugs identified by the community and by us at LINBIT, as we
use more and more LLMs to analyze events in DRBD clusters.

This is a release candidate. Please test it.


9.3.5-rc.1 (api:genl2/proto:86-101,118-125/transport:23)
--------
 * Track changed blocks for incremental backups: a tracking bitmap slot
   records every write to the backing device; cbt-flush and cbt-start
   bracket a snapshot taken while I/O is suspended on all nodes
 * suspend-io now also waits for the barrier ack of the last epoch, so
   that with protocols A and B the writes are on the peers' stable
   storage too; flush-to-peers=3Dno skips that wait
 * Add rdma2, a new RDMA transport that moves all data with one-sided
   RDMA-WRITE, sends bios zero-copy, and fails over to a surviving path
   when a link goes down
 * Serve the new drbd2 netlink family next to the drbd family
 * Optionally serve DRBD 8.4 userland over the netlink family at version
   1 (CONFIG_DRBD_NL_DRBD1, rpmbuild --with nl_drbd1,
   DEB_BUILD_OPTIONS=3Dnl_drbd1); off by default
 * Fix lb-tcp skipping a path for good after the peer closed it first
   during a disconnect, which starved every later handshake
 * Fix spurious and racy "bitmap locked" warnings when bitmap operations
   on different peer slots run concurrently
 * All fixes from 9.2.21-rc.1
  - Fix a resync target staying Inconsistent with nothing left to sync:
    when the Primary cannot reach the sync source, after aborting a weak
    sync source, and when P_RS_CANCEL_AHEAD overtakes the Ahead state
    change
  - Fix a reconciliation resync target waiting in WFBitMapT forever, and
    out-of-sync bits from before a lost diskless Primary being dropped at
    equal dagtags
  - Fix a peer's connect-time upgrade from Outdated going unnoticed,
    which left writes unreplicated
  - Fix an Outdated sync source being marked UpToDate after a resync
    with failed blocks
  - Fix the day0 slots, a regression in 9.2.20: forget-peer left a slot
    that the next UUID bump filled with a later generation, and a peer
    created from the day0 UUID could be refused as unrelated data;
    attach repairs such meta data
  - Fix promoting a peer that holds an older generation of the data a
    diskless Primary exposes
  - Fix P_OUT_OF_SYNC: never sent for Primaries with node-id 8 or higher,
    a crash after del-peer of a Primary, and writes left pending for a
    peer that lost its connection
  - Fix the activity log: AL updates turned off while a crashed Primary
    resyncs, the superblock written too late on "al-updates no", and the
    in-core AL not written when AL updates come back on
  - Fix a dry-run connect (--tentative) establishing the connection
    without a resync
  - Fix the last close returning before the peers have the last write on
    stable storage, and auto-demote failing on a pending signal
  - Fix call-pri-lost-after-sb killing the receiver instead of demoting
  - Fix online resize: drain application I/O before the commit and before
    a participant replies, cache the peers' size answers per volume, and
    refuse a too small peer while syncing from a larger one
  - Fix a receiver deadlock at the end of a resync when the link fails
    while the bitmap is written, and bound the memory a bitmap write-out
    holds
  - Fix resync pacing: the fixed resync-rate (c-plan-ahead 0) holds, the
    resync queue at the backing device is bounded so application I/O does
    not wait behind it, and DRBD logs when max-buffers or c-max-rate
    limit a resync
  - Fix connect and disconnect issues: a spurious NetworkFailure right
    after a handshake, a stale ping timeout dropping the next connect, a
    peer's close while connecting taken as a network error, ko-count 0
    being counted down, and a second peer accepted beside a DRBD 8.4 peer
  - Fix lb-tcp: a NULL pointer dereference in the receiver, a CPU spin
    when the peer closes mid-payload, zero-length data chunks, hot-adding
    paths, and listeners left on unused paths
  - Fix rdma: use-after-free and refcount underflows on teardown during
    connect, a 60 s hang after a failed establish, going StandAlone on an
    interrupted connect, and a crash with a peer running rdma2
  - Fix the TLS handshake compat code (upstream fixes): leaks, refcount
    and use-after-free bugs, and a missing admin check on DONE
  - Fix memory corruption by peer_device flags on 32-bit kernels
  - Fix a negative ap-in-flight after a resend, BarrierAck count warnings,
    sending on after a send failed, and an unsent packet flushed at
    disconnect ("Wrong magic value" on the peer)
  - Fix attach hanging after the node was a verify target, and a double
    release when linking the holder fails
  - Show the submit and sent ages of requests in debugfs again, and mark
    peer writes that completed locally
  - Fix building SUSE KMPs on SLES 16, and the build with
    CONFIG_DRBD_TIMING_STATS

https://pkg.linbit.com/downloads/drbd/9/drbd-9.3.5-rc.1.tar.gz
https://github.com/LINBIT/drbd/commit/1f0b40d862abd8246f3d29a7576fd35b9d1f3=
fa2

https://pkg.linbit.com/downloads/drbd/9/drbd-9.2.21-rc.1.tar.gz
https://github.com/LINBIT/drbd/commit/e9d24675bf6f1679f4bfde4c6cb38ac9271b5=
af4

cheers,
 Philipp