hi
I have some questions with regards to iscsi volume replication
- i have 2 san with open-e v6.0up40.8101.4550 64bit
- 1 san is in the office data centre and the other in the DR site
- i have a 10mb WAN link between the 2 sites
- i have setup various 10GB volumes and they each contain 1 vm (xenserver 5.6)
i have setup replication jobs for each of the volumes and set the source and destination etc.
my first question is the following:
1) when setting up replication of the volumes of 10gb the initial replication replicates the full 50gb (according to the task status) although it contains no data. is this expected behaviour?
2nd question has to do with additional replication after initial replication.
- when i add the volume to my xenserver and replicate it replicates about 100mb of additional data
- when i put a 8gb virtual machine on the volume (with 3.5gb of data and replicate it only replicates the 3.5gb (which is good)
- i then stop volume replication, make the destination volume a source, mount it in xenserver and i can access the virtual machine, after making some slight tweaks i run the reverse replication job (on the primary i toggle source to destination) but to my surprise it replicates the full 10gb volume and not just the changes. I did select clear metadata and perhaps i should not have done that?
- once the volume has replicated back to the office datacentre i change destination/source again on both san's and again the volume replication replicates the full 10gb volume.
The above is a test setup but once i go live i will have 5x 100gb volumes and if replication is so inefficient over a 10mb link (even 100mb would be slow) the initial replication is going to take weeks and if i ever have to failover to the DR site and failback afterwards it is going to take weeks again to replicate the data back.
the other thing is that during the initial replication the vm's become unusable, i found another thread on this forum about i/o write speed dropping and making vmalloc changes but as i have a 64 bit system this will not work
sorry many questions but i would like figure out how i can make volume replication more efficient (only replicating changed bits rather than all of them) and how i can keep vm's up and running and working during the intial replication (and failback replication as well)
many thanks for your help!