Message-ID: <7AD2D6DC-0609-42F9-A481-B6E5C0F58180@amazon.com>
Date:   Wed, 30 Mar 2022 19:31:32 +0000
From:   "Kiselev, Oleg" <okiselev@...zon.com>
To:     Philipp Reisner <philipp.reisner@...bit.com>,
        Jens Axboe <axboe@...nel.dk>
CC:     "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Lars Ellenberg <lars.ellenberg@...bit.com>,
        Christoph Hellwig <hch@....de>,
        "drbd-dev@...ts.linbit.com" <drbd-dev@...ts.linbit.com>,
        "Herrenschmidt, Benjamin" <benh@...zon.com>,
        "Smith, Stewart" <trawets@...zon.com>
Subject: Re: [Drbd-dev] state of drbd in mainline

AWS RDS is a major user of drbd.  We are probably responsible for the substantial percentage of drbd users in the world.  We are currently on drbd-8.4.  We will eventually migrate to drbd-9, but at our scale this isn't going to happen very soon.  

The last time we needed to patch drbd was back in 2018.  We've not diagnosed any reportable issues with drbd-8.4 in the past ~4 years.   It's a stable, mature driver.   We would prefer for drbd-8 to continue being available in the upstream tree.  We'd also welcome drbd-9 being available in-tree as soon as possible: it will make life much easier for other AWS teams that are currently working on DRBD deployment.

On 3/30/22, 8:24 AM, "drbd-dev-bounces@...ts.linbit.com on behalf of Philipp Reisner" <drbd-dev-bounces@...ts.linbit.com on behalf of philipp.reisner@...bit.com> wrote:

    CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe.



    > > Jens, my intention is to keep it in-tree, and at some point update it.
    > > Regarding your questions:
    >
    > That'd be great, but it's been years since there was any significant
    > updates to the in-kernel drbd... I would strongly suggest that the
    > in-kernel be brought closer to what people are mostly running, as it
    > stands it's basically unmaintained.

    The changes we worked on over many Years in the more recent drbd-9.x
    branches are just too fundamental to do them in small chunks, we could
    upstream bit by bit.  We need to get that reviewed in a big series.  If I
    started to dump them on linux-block right away, nobody would look at it
    seriously, since it would be too much.  I intend to get people from red
    hat/suse assigned to do such a review. Then we will do that on linux-block,
    so that everyone who cares sees what happens.

    [...]
    > The main discrepancy here is that there are apparently huge numbers of
    > in-tree users, yet no fixes or patches at all making it to mainline.
    > Either drbd is bug free and doesn't require any fixes at all, which I
    > very much would doubt, or fixes aren't being sent upstream.

    It is the broad consent among the users of the drbd-8.4 branch (that is what
    is in-tree), is that it works for its purpose. It is for sure not bug-free,
    but people are not running into bugs anymore. So, call it free of relevant
    bugs, if you want.  No new features go into that branch, on purpose. To keep
    it that way.

    Have a look at that one real bug-fix that was identified in the last Year.
    20210426163032.3454129-1-christoph.boehmwalder@...bit.com <https://patchwork.kernel.org/project/linux-block/patch/<a href=>/">https://patchwork.kernel.org/project/linux-block/patch/20210426163032.3454129-1-christoph.boehmwalder@linbit.com/

    When do you want to have that reposted to you?
    right now? Just before the next merge window opens?
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