[DRBD-user] Question about server structure

Tim Mauerbach tim.mauerbach at googlemail.com
Thu Dec 23 21:24:07 CET 2010

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


2010/12/23 J. Ryan Earl <oss at jryanearl.us>

> On Thu, Dec 23, 2010 at 11:23 AM, Tim Mauerbach <
> tim.mauerbach at googlemail.com> wrote:
>
>> I am thinking about the structure of a new mailserver on top of
>> raid1/lvm/xen.
>>
>> Two different approaches come to my mind:
>>
>> 1. One big LV as DRBD backing device for the whole guest (os + data).
>> 2. One small LV without drbd for the base system + one big LV as DRBD
>> backing device only for data (maildirs+mariadb).
>>
>> Is the maintenance overhead of 2 worth the performance gain?
>>
>
> I'd definitely go with 1, and it has nothing to do with performance.  If
> you put the whole VM on top of DRBD, and then make that a primary/primary
> (aka active/active) DRBD then you can live-migrate the VM between host
> and/or use Remus VM-mirroring for VM-HA.  I don't see why anyone would ever
> go with 2 as leaving the OS unreplicated on the small LV exposes you to big
> potential downtime as you rebuild a new OS for the replicated-data in the
> event of a failure.  Am I misinterpreting what you mean?
>
> -JR
>
Thanks for your input.
You´re right. It has nothing to do with performance, I meant efficiency:

The idea of 2 is to prevent live-replication of not that important non-user
data (os + tmp|log files) that could be replicated via rsync at midnight.
Thus I could use my DRBD capacity more efficiently and only for important
data, though at the expense of maintainability.

Best Regards
Tim
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