Re: [Xen-devel] [PATCH 2 of 2 V3] libxl: Remus - xl remus command

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2012-02-03 at 07:00 +0000, rshriram@xxxxxxxxx wrote:
> # HG changeset patch
> # User Shriram Rajagopalan <rshriram@xxxxxxxxx>
> # Date 1328251593 28800
> # Node ID 2965835b0c0062a359ac04c715d7af52c6ba60ee
> # Parent  90e59c643c00c079996e13b75f89d1f0cd931a02
> libxl: Remus - xl remus command
> 
> xl remus acts as a frontend to enable remus for a given domain.
>  * At the moment, only memory checkpointing and blackhole replication is
>    supported. Support for disk checkpointing and network buffering will
>    be added in future.

>  * Replication is done over ssh connection currently (like live migration
>    with xl). Future versions will have an option to use simple tcp socket
>    based replication channel (for both Remus & live migration).
> 
> Signed-off-by: Shriram Rajagopalan <rshriram@xxxxxxxxx>
> 
> diff -r 90e59c643c00 -r 2965835b0c00 docs/man/xl.pod.1
> --- a/docs/man/xl.pod.1       Thu Feb 02 22:46:33 2012 -0800
> +++ b/docs/man/xl.pod.1       Thu Feb 02 22:46:33 2012 -0800
> @@ -348,6 +348,39 @@ Send <config> instead of config file fro
>  
>  =back
>  
> +=item B<remus> [I<OPTIONS>] I<domain-id> I<host>
> +
> +Enable Remus HA for domain. By default B<xl> relies on ssh as a transport 
> mechanism
> +between the two hosts.
> +
> +B<OPTIONS>
> +
> +=over 4
> +
> +=item B<-i> I<MS>
> +
> +Checkpoint domain memory every MS milliseconds (default 200ms).
> +
> +=item B<-b>
> +
> +Replicate memory checkpoints to /dev/null (blackhole).

Is blackhole replication just a debug thing? If so would be useful to
say so, if not then explaining when/why I might use this option would be
helpful.

> +        /*
> +         * TODO: change this to plain TCP socket based channel
> +         * instead of SSH. For both live-migration and Remus.
> +         */

IMHO comments like "TODO: split brain" are OK, because they highlight
fairly critical missing pieces, but in general I don't think we need to
track everything which might potentially happen to the code in the
future as TODO comments. Just add it to your own TODO list.

o/w looks good, thanks.

Ian.



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