Storage-based data replication
Hi, storage-based data replication still seems to be a challange, even in SC 3.2. I found this link http://blogs.sun.com/SC/entry/sun_cluster_3.2,_truecopy,_and which includes the following "Previously(...before SC3.2...) , only Veritas Volume Manager (VxVM) could be used with Sun Cluster and Truecopy." Unfortunately there is just very few documentation about Storage-based replication and I found nothing regarding the use of VxVM and replication in SC 3.1. Is this really supported ? If yes, are there any experiences or any documentation. Ok, there is a blueprint from 2003, but this does not cover SC and seems to be outdated (in terms of SVM and VxVM). Concretely I'm looking for a supported soltution to make use of storage-based data replication using two HP EVA 3000 systems. The SC nodes are connected by secure path. Today to avoide any SC reconfigurations the securepath driver needs to be reconfigured and all clusternodes have to be rebootet in case of a storage failover, but for me that's just a workaround. Any hints or experiences ? Thanks, Marc
[1073 byte] By [
mneitznera] at [2007-11-26 21:21:33]
# 1
Well, the cited paragraph really refers to the usage of Truecopy to replicate a volume to a node outside the cluster (or a different cluster) - and that in that case only VxVM was really feasable. SVM really needed additional steps involving basicly recreating the diskset, which is not nice.
SC 3.2 really introduced the capability to actually substitute host based mirroring with Truecopy, if SE99xx storage gets used.
So to answer your question - SC 3.1 does not support substituting host based mirroring with Truecopy. But you could replicate a volume used by the cluster to a different node not part of this cluster.
For your last part of the question, I am not sure if HP EVA 3000 are supported together with secure path (not knowing what it is) and truecopy. That is something to check with the open storage page (http://www.sun.com/software/cluster/osp/).
On storage based replication within Sun Cluster 3.2 you can find some more details on http://docs.sun.com/app/docs/doc/819-2971/6n57mi28m?a=view
Greets
Thorsten
# 2
Marc,
The situation is as follows:
1. You can use TrueCopy replication in place of host based mirroring within a single cluster running SC3.2. This cannot support Oracle RAC because the promotion of secondary to primary is not transparent. You cannot use arbitray 3rd party storage replication inside a cluster without substantial hacking!
2. You can use TrueCopy (or SRDF) to replicate data between Sun Clusters running Sun Cluster Geographic Edition. You are currently limited to VxVM as a host based volume manager (or using hardware RAID). Of course, you can construct your own hand crafted solution using any 3rd party storage replication between clusters so long as the 3rd party vendor supports it.
In general, I would not recommend replication instead of mirroring inside a cluster. To me, this adds complexity and increased complexity usually leads to lower availability. Here, the complexity is that you are trying to make a replication product look like a mirroring solution. Unfortunately, it lacks the transparent, seamless access to the secondary data.
Tim
