Just a few weeks ago I wrote an article about how to configure the iSCSI Software Target 3.3 in a cluster environment. While it is great for labs and testing, up until today it was not supported in a production environment. Well…that all changes today! Microsoft just announced that the iSCSI Software Target 3.3 is a freely available download and can be used on a production network.
This all starts to get interesting once you start considering the possibility of building shared nothing iSCSI Target clusters with DataKeeper Cluster Edition. Build 2-nodes locally for HA and then place a 3rd one in a remote data center for disaster recovery. Now that is a pretty sweet HA/DR solution without having to break the bank!
Clustering For Mere Mortals 
Great blog – but can you please explain what you mean by ‘share nothing’ iscsi target clusters? I’m also curious what you would consider the next best alternative to datakeeper that really would ‘break the bank’?
Thanks!
Chris
I’ll write another article on shared-nothing iSCSI target clusters…I’m hoping that Microsoft will provide a fix that makes the iSCSI Virtual Disk cluster resource compatible host based multisite cluster solutions which would enable you to build a highly available iSCSI target cluster. As it is now you have to run the multisite cluster replication software within the servers connecting to the iSCSI target in order to build multisite clusters. This is an excellent solution, but one thing that is missing is support for CSV. If we could run within the iSCSI target I would think that we could build mulisite clusters that support CSV.
As far as breaking the bank, you could spend anywhere from hundreds of thousands of dollars for enterprise class SANs and array based replication all the way down to more simple backup/replication solutions such as DPM or even Starwind replicated iSCSI target clusters. I’m not sure of the price of those solutions, but I know once the Microsoft iSCSI Software target solution supports multisite cluster replication software like DataKeeper it will be hard to beat in terms of features at the same price point.
Thanks David – on another note, is SIOS still open for business? We put an inquiry in with them a few days ago – then we tried calling them on Thursday – but only got voicemail on all extensions – left a msg and email but still no reply. Thx! Chris
Maybe this is what you are describing (I’m a bit confused with all of the terminology), but would it be possible to mirror the disk that contains the iSCSI target(s)? That is, run Datakeeper on the server acting as the target? Wouldn’t that mirror everything at a lower level, including CSVs?
Again, sorry if this is what you are saying.
Yes, that is right. It will work even better once Microsoft releases a hotfix so the virtual disk cluster resource works with DataKeeper. Once that is fixed you can build highly available iSCSI targets without shared storage.
Thanks Dave. I’m still a bit fuzzy with the terms, but as I understand it, it is currently possible to:
1) Build a Windows Server 2008 R2 server. 2) Install the iSCSI target software on it.
3) Create necessary targets, including CSVs.
4) Mirror the disk containing the targets to another server using DataKeeper.
5) If the primary server fails, manually redirect the cluster to iSCSI targets on the backup server.
Would that work? I’m trying to figure out the absolute cheapest way to do failover.
Thanks again.
Ceth – you are correct, glad we could connect offline.
I’m confused, if you’re talking about running iSCSI traffic over a WAN for DR then you’ll be sorely disappointed at the performance. Even if you were talking about heartbeat traffic (and some type of sideband file update mechanism like one-way DFS replication) there are issues with latency and your cluster going split-brain when the remote node doesn’t get a heartbeat packet within the threshold. Not to mention the security issues of sending straight iSCSI traffic over a WAN.
Could you maybe clarify what you meant in the last paragraph of your post? I’m not familiar with Datakeeper and as fancy as that product might be, I don’t see it overcoming the latency and bandwidth issues when dealing with iSCSI.
no, the iscsi targets are all local, DataKeeper uses block level asynchronous replication to keep the data in sync between sites, so WAN latency does not impact performance.