[DRBD-user] drbd solution for distant sites ? (4MB line)

paddy paddy at panici.net
Fri Feb 24 12:56:08 CET 2006

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


On Thu, Feb 23, 2006 at 05:28:14PM +0100, Romain BOTTAN wrote:
> Hello,
> I know drbd for just one month,
> I've set up cluster solutions with heartbeat and drbd, all works well 
> with a gigabit link to play with file sync.
> 
> Now they want to put some distance between the two nodes -- just 700 Kms :)
> the link will be a vpn connection up to 2 or 4 MB :(

the infamous 'they' ;)

I've been running a 2G drbd on a non-dedicated network for a little while
now, but I don't have your distance based latency problem.

I can vouch that drbd will work just fine at 8MB (assuming you can live
inside that bandwidth).

If the link between your two machines is not dedicated or of guaranteed
bandwidth then congestion on the intermediate network may be a factor
to consider in your calculations.

> I've made some computes and as there is some 400 GB to synchronize, it 
> takes minimum 18 days to make the first sync if we stay in 2MB :(
> After this period I expect that synchronization would ask for less 
> resources... but is DRBD capable to function with such a link ?
> 
> I would know if DRBD is a good solution for my problem or we need to use 
> another way to make a common file server synchronized for our two sites.

You haven't really told us much about what you need it to do, and 
"common file server" suggests you might be looking for something
more like AFS or Coda, or even something more tightly coupled.
What will happen when both servers are up ? what will happen when
one goes down ?

On the question of ip fail-over.  If you found you couldn't do that
(and vpn suggests this may not be a problem), then you could consider
solutions using dns or (I think) routing.

Regards,
Paddy
-- 
Perl 6 will give you the big knob. -- Larry Wall



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