Subject: Re: [vserver] Re: [Freedombox-discuss] [vserver] Re: A software architecture for the FreedomBox
From: Jon Bendtsen <jbendtsen@laerdal.dk>
Date: Fri, 15 Apr 2011 12:09:55 +0200

 Fri, 15 Apr 2011 12:09:55 +0200
On 15/04/2011, at 01.01, Martin Fick wrote:

> --- On Thu, 4/14/11, Gordan Bobic <gordan@bobich.net> wrote:
>>> --- On Thu, 4/14/11, Gordan Bobic<gordan@bobich.net>
>> 

[cuuuuuut]


>> However
>> - what use-case do you have where one guest will fail
>> unrecoverably on one machine but resumes working on another
>> machine with the exact same FS? In what case would a single
>> guest fail without all of them failing?
> 
> Think load balancing.  Say 10 vservers, split them
> so that 5 run on each host normally.  If either host
> goes down, the other one picks up the slack.
> Everything runs slower, but at least it still runs.

I think about the same considerations at the moment, planning a new setup.

Why not make 2 DRBD shares, A and B, put half of the vserver guests on the A storage,
unify, them, and then put the other half on the B share. All the vserver guests on the
A DRBD share runs on the A-host, and like wise with the B host. In daily usage you have
no open files from the B share on the A host, so all the memory would be unified. In
case of a split brain you can keep the guests running, and once you get connection again
easily resync the DRBD.

In case of 1 vserver host failing then you can just start all the vserver guests in
DRBD share A on the vserver host B. Yes that will not unify both groups of hosts, but
that should only be until you get the A host up again.

So, what do you think?


JonB