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 12:27:21 +0200

 Fri, 15 Apr 2011 12:27:21 +0200
On 15/04/2011, at 12.20, Gordan Bobic wrote:

> Jon Bendtsen wrote:
>> 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?
> 
> I still don't see the advantage of using DRBD for block-level replication here. The
extra complication of having to deal with FS level fail-over doesn't seem to buy you
anything compared to the lsyncd mirroring setup.

can you guide me to a good lsyncd howto?

can lsyncd replicate ACL? Can it replicate non linux vserver guests? (i'd rather have
one sync system that does it all, than having multiple systems)




JonB