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Re: non-standard TCP tunings in EC2 images

On 2016-07-20 11:45:27, Lucas Nussbaum wrote:
> On 20/07/16 at 11:26 +0200, Thomas Lange wrote:
> > 
> > Using tasksel we already have different flavours of Debian
> > installations. Why not see the cloud images as another flavour, which
> > besides having some additional packages installed also tune some
> > parameters for best practice in a cloud environment.

But there is no split like in Ubuntu case for desktop, server and cloud and I'm
not sure that I want to go this direction in that way Canonical did it.

> I'm curious about why the sysctl settings I quoted are considered best
> practices in cloud environments, and not in other environments
> (including standard server environments)?

Example setting up swappiness to 0 is reasonable as there is no swap by default
on cloud instances.
I'd say other options are just set that way so no manual adjustments need to be
done to have instance provisioned in the automated way and operational straight
away for most of the 'cloud' purposes.
And as those instances are coming and going sometimes quite fast this IMO seams
to be reasonable approach.

But also I have to say that when I'm creating envs based on Debian AMIs (AWS)
I'm copying default AMI provided by Debian so I have it under my control in the
event Debian will decide to retire AMI and my users won't adjust scripts to
accommodate this change.
Copying and adjusting AMI with ex. new sysctl settings and keeping it on my
own account is something I do frequently. This type of practice would allow
Debian images to be closer to the 'non cloud' official image but it'd be hard
to enforce and will generate additional costs on our users (image storage).

> I'm not against having a discussion about Debian providing different
> kernel settings profiles for different environments. This is something
> that could probably be useful (those settings can be configured for a
> reason, after all).
> However, I don't think that this is something that should be decided
> silently by the cloud team on its own, but rather discussed with the
> kernel team to find a solution that works for everybody.

There is no one solution which will fit all (ex. kernels for cloud and RT) in
relation to kernel settings, so I wouldn't count on this, but I agree that
input from kernel team may be beneficial.

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