Monday, March 22, 2010

Cheapskate Multi-site Cluster for Hyper-V R2 HA

MS W2K8 R2 announces 2 important new HA features for virtualization: (1) new cluster shared volume (CSV) for Hyper-V HA cluster & live migration and (2) multi-site clustering.

Hyper-V R2 cluster support VM HA & live migration using the Cluster Shared Volume (CSV). CSV is still a shared volume between 2 nodes, except that 2 nodes can own the volume concurrently (instead of single node ownership previously). You may have a single large CSV that stores multiple VHDs and load balance the VMs within the cluster. However, the common shared CSV is still the major single point of site failure (imagine a total site outage e.g. earthquake, power, flood etc).

On the other hand, multi-site clustering can solve the above site disaster issue - each server node owns its storage on one site & replication occurs between the differently located storage box. One site is defined as source storage and the other as target storage. It presents a single virtual volume to a pair of cluster. However, CSV does not support replicated volumes. Hence, only node may own this virtual LUN at any one time. Two types of replication exist - host-based and storage-based. Multi-site clustering supports Hyper-V R2. The recommended quorum type for this setup is "Node and File-share (instead of disk) majority" whereby the file share server also carry a vote. For better resiliency, the file share server is recommended to be hosted at the third site.

I found this online demo that used host-based replication solution - a software called "SteelEye Data Keeper Cluster". As compared to expensive SAN replication solution, an advantage of this software is the retrofitting of any existing storage, as it allows mirroring across different storage types & volume e.g. iSCSI to NAS, DAS to iSCSI etc.

1 comment:

    i made this video, please let me know if there are any errors and make a comment on the page. Thanks! I am new to this