linux-kernel - Re: [PATCH 0/1] block io layer filters api

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Message-ID: <b99a1577-6f39-9228-d176-5a8bc38bd64d@acm.org>
Date:   Tue, 1 Sep 2020 08:34:17 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Sergei Shtepa <sergei.shtepa@...am.com>,
        Jens Axboe <axboe@...nel.dk>
Cc:     "masahiroy@...nel.org" <masahiroy@...nel.org>,
        "michal.lkml@...kovi.net" <michal.lkml@...kovi.net>,
        "koct9i@...il.com" <koct9i@...il.com>,
        "jack@...e.cz" <jack@...e.cz>,
        "damien.lemoal@....com" <damien.lemoal@....com>,
        "ming.lei@...hat.com" <ming.lei@...hat.com>,
        "steve@....org" <steve@....org>,
        "linux-kbuild@...r.kernel.org" <linux-kbuild@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>
Subject: Re: [PATCH 0/1] block io layer filters api

On 2020-09-01 06:29, Sergei Shtepa wrote:
> However, the same time requirement also presents a big immediate problem -
> as until this is done, over a hundred thousands of Linux users will not be
> able to protect their servers running the impacted kernels
> (our backup agent is free).
> They will be forced to stop using the new version of the kernel
> (or take a risk of data loss).

How can backup software work at the block layer level without any cooperation
of higher layers? How is it e.g. guaranteed that backups are crash-consistent?

What happens if the network connection with the backup server is lost? How
much time is needed to recover after the network connection has been restored?
Does the contents of the entire block device has to be resent to the backup
server?

Thanks,

Bart.