[jboss-jira] [JBoss JIRA] (JGRP-1680) RDMA based transport

[Bela Ban (Jira)]

    [ https://issues.jboss.org/browse/JGRP-1680?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13653502#comment-13653502 ] 

Bela Ban commented on JGRP-1680:
--------------------------------

https://stackoverflow.com/questions/7820124/how-to-use-dma-or-rdma-in-java

> RDMA based transport
> --------------------
>
>                 Key: JGRP-1680
>                 URL: https://issues.jboss.org/browse/JGRP-1680
>             Project: JGroups
>          Issue Type: Feature Request
>            Reporter: Bela Ban
>            Assignee: Bela Ban
>            Priority: Major
>             Fix For: 5.0
>
>
> Investigate whether an RDMA based transport makes sense.
> Advantages:
> * Speed, low latency (TCP/IP is bypassed entirely)
> * Low CPU usage
> Disadvantages:
> * JNI/C code
> ** Such a transport implementation would have to live outside of the JGroups repo
> ** Maintainability nightmare: the C code would also have to be ported to various OSes
> *** Investigate Java based libs (IBM's jVerbs) and C based libs (Apache Portable Runtime?)
> * High memory use, growing with cluster size: similarly to TCP, a 'group multicast' would involve N-1 sends. RDMA requires a Queue Pair (QP) for each destination. Each QP requires pinned memory (receive and send buffer), so each node would have to reserve (pin) N-1 memory buffers [1]
> ** OTOH, we may not use many group multicasts, e.g. with Infinispan's partial replication (DIST mode)
> * High cost of RDMA adapters, NICs and wiring: only a very small fraction of users would run such a transport.
> [1] http://www.hpcwire.com/hpcwire/2006-08-18/a_critique_of_rdma-1.html



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