Re: [Xen-devel] [PATCH 4 of 4 V5] tools/xl: Remus - Network buffering cmdline switch

[Shriram Rajagopalan <rshriram@xxxxxxxxx>]

On Mon, Nov 25, 2013 at 7:37 AM, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx> wrote:

Shriram Rajagopalan writes ("[PATCH 4 of 4 V5] tools/xl: Remus - Network buffering cmdline switch"):

> tools/xl: Remus - Network buffering cmdline switch
>
> Command line switch to 'xl remus' command, to enable network buffering.
> Pass on this flag to libxl so that it can act accordingly.
> Also update man pages to reflect the addition of a new option to
> 'xl remus' command.

Shouldn't enabling network buffering be the default ?

Given that network buffering support is conditionally compiled into

libxl, it makes sense to let the user explicitly enable network buffering.

If network buffering was enabled by default, but libxl was missing the feature,

then running xl remus (without any option) would immediately fail saying network 

buffering support is missing. Might as well make people enable it explicitly and 

then discover the lack of support for it inside libxl. 

 

Is it really useful to have a command-line option to change the script ?

That was added on Ian C's suggestion. It might be useful if people have 

openvswitch based setups and want to tweak the network buffering setup.

 

> diff -r 94eea030e009 -r 3c11efb5e8fe docs/man/xl.pod.1
> --- a/docs/man/xl.pod.1       Mon Nov 18 11:10:02 2013 -0800
> +++ b/docs/man/xl.pod.1       Mon Nov 18 11:46:55 2013 -0800
> @@ -398,8 +398,7 @@ Print huge (!) amount of debug during th
>  Enable Remus HA for domain. By default B<xl> relies on ssh as a transport
>  mechanism between the two hosts.
>
> -N.B: Remus support in xl is still in experimental (proof-of-concept) phase.
> -     There is no support for network or disk buffering at the moment.
> +N.B: There is no support for disk buffering at the moment.

I think you need to keep the "experimental (proof-of-concept)" note.
Without disk buffering, surely any VM which uses remus might corrupt
its disk ?

agreed.

 

> +=item B<-n>
> +
> +Enable network output buffering.  The default script used to configure
> +network buffering is /etc/xen/scripts/remus-netbuf-setup. If you wish to
> +use a custom script, use the I<-N> option or set the global variable
> +I<remus.default.netbufscript> in /etc/xen/xl.conf to point to your script.

There is no need to mention the default script again in this
paragraph.

I seem to have missed something, but should it be possible to specify
the script individually per domain ?

using the -N option.

 

Ian.

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