[Devel] [PATCH RH9] dm-ploop: port the standby mode feature.

[Kui Liu]

-----Original Message-----
From: Alexander Atanasov <alexander.atanasov at virtuozzo.com>
Date: Friday, 21 October 2022 at 7:35 PM
To: Kui Liu <Kui.Liu at acronis.com>, Konstantin Khorenko <khorenko at virtuozzo.com>, Alexey Kuznetsov <kuznet at acronis.com>
Cc: Devel <devel at openvz.org>
Subject: Re: [Devel] [PATCH RH9] dm-ploop: port the standby mode feature.

    On 21.10.22 14:28, Kui Liu wrote:
    >      >      >      Ok - for the user space there are two options:
    >      >      >          1. add an argument to enable at creation time
    >      >      >          2. command standby_enable /if using the enable it is possible to
    >      >      >      implement a disable command too/.
    >      >      >
    >      >      >      I prefer the second approach but let's hear other opinions too.
    >      >      >      And yes we can possibly do both but is there a use case ?
    >      >      >
    >      >      > [LIU]: Since the static key is a global option, I also think the second approach is better.
    >      >      > In case of nodes with vStorage + ploop + iSCSI setup, we just need to enable the static
    >      >      > key early in system init or iSCSI service init.  I don't think it is necessary to implement both.
    >      >
    >      >      You are right. It will need at least one ploop device created to issue a
    >      >      device mapper command to enable standby. Would a module parameter work?
    >      >
    >      > [LIU] Yes, I think it is better to make the static key a module parameter.
    > 
    >      This rised a question - how and who will pass the module parameter when
    >      required ? How we will handle the existin users ? What do you think ?
    > 
    > [LIU]: Like add a conf file ploop.conf in /etc/modprobe.d or lib/modeprobe.d? This conf file can be shipped with the release image, or installed later.  Are you referring to VZ7 as existing users? I saw you also made the changes to VZ7, but I'm not sure whether it is necessary to backport these changes to VZ7.

    Yes, VZ7 users - there are issues related to it so trying to fix them. 
    the modprobe.d would do but do you have a package that can install the 
    conf tied to the iSCSI target, so it gets installed only if the iSCSI is 
    used ?

[LIU]: Yes, we do build the our own SCST package, so we can install the conf from there.   

    -- 
    Regards,
    Alexander Atanasov