[DRBD-user] Corosync Configuration

Helmut Wollmersdorfer helmut.wollmersdorfer at fixpunkt.de
Wed Jun 13 18:46:44 CEST 2012

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


Am 13.06.2012 um 17:45 schrieb Arnold Krille:

> On Wednesday 13 June 2012 09:26:45 Felix Frank wrote:
>> On 06/12/2012 08:23 PM, Dennis Jacobfeuerborn wrote:
>>>> Don't use crossover cables.. In my experience use crossover  
>>>> cables for
>>>> two
>>>>
>>>>> node cluster make only problems... use a simple switch..
>>>
>>> Why would a setup with 2 cables and a switch be more reliable than  
>>> just a
>>> single cable? That doesn't make sense.
>>
>> Uhm, I don't think that was Eduardo was suggesting.
>>
>> Someone on this list (Digimer?) has made a good point some time about
>> switches allowing for better forensics in case of link problems  
>> (i.e.,
>> the switch can help you identify the side with a faulty NIC/cable).
>>
>> On the other hand, a switch introduces one more (two really, counting
>> the extra required cable) possible point of replication failure. I've
>> never had negative experiences with back-to-back connections either.
>
> A switch also has input- and output-buffers introducing another step  
> of
> latency.
>
> We would use a direct link-cable if that scaled for more then 2  
> servers. (We
> actually though about just adding more network-cards, connect three  
> servers
> with three cables directly and use bridges with (r)stp for the  
> storage ring.
> But now we will just use the additional cards for more redundancy to  
> have
> trunked connections to two switches...)


Two switches can also be a problem:

We have bonding with 2 interfaces connected to 2 switches, each switch  
connected to a different uplink in HSRP mode. Some weeks ago we  
experienced high packet loss with the result, that the delivered web- 
services were more or less unusable. After change of the switches the  
problems were gone.

For the direct cluster connection we have 2 bonded Gbit-interfaces,  
but one connection only runs on 100 Mbit. Maybe a switch would help in  
this case for diagnosis. But I will just put additional 2 interfaces  
into the nodes.

Helmut Wollmersdorfer




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