On 11/30/2010 12:02 PM, Wez Furlong wrote:
> Hey folks,
> 
> We use the agreed messaging mode of spread for coordinating nodes in our 
> cluster, and I've just discovered corosync.  We have a love-hate relationship 
> with the spread software, and the possibility of moving to another system 
> with similar facilities is appealing to us (but at the same time, we're not 
> going to blindly leap!)
>

Which parts of spread don't you like?  The main problem we had with
spread was the license which made it unsuitable for use in open source
distributions.

> The evs_overview(8) docs suggest that EVS is not currently ready for prime 
> time, so I'm wondering which aspects of it need work?
> 

Documentation in corosync is pretty weak and out of date.  We spent our
time writing good code instead ;)  We hope to address the documentation
issues in the future now that the code is quite stable.

EVS is primetime - the api is very simple.  We do recommend people use
the CPG api (man cpg_overview) because it is where we intend to do our
future development.

> We make use of the spread SP_join, SP_leave APIs, (analagous to evs_join, 
> evs_leave?) and SP_scat_multicast, SP_scat_receive 
> (evs_mcast_joined/evs_mcast_groups and the deliver_fn callback specified in 
> evs_initialize).  Are my assumptions about the mapping of APIs from spread to 
> corosync accurate?  Are there specific nuances that should be taken into 
> account when migrating from spread?
> 
> Another capability that we use in spread is the ability to run the spread 
> daemon on two different networks (often in different datacenters) and let 
> spread route the messages to the appropriate groups.  We tend to use 
> broadcast rather than multicast.  I didn't see specific documentation on this 
> (I did notice the "broadcast" option in corosync.conf), so I'm wondering if 
> the features are on par with spread or if there are some differences that 
> we'd need to take into account.
> 

Corosync supports native rdma, udp broadcast, udp multicast, and udp
unicast transports.  Unlike spread, corosync is designed to only work
within a LAN and as a result, there is higher latency when using over
long haul networks.

Regards
-steve

> Thanks in advance for any information you can provide,
> 
> --Wez.
> 
> 
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