We are in the process of migrating storage from one array to another. I know the commands I would use in LVM but I am not very familiar with VxVM.
The goal is to attach the new LUNs from the new array and add them to the disk group. Then mirror the data online to these new LUNs using VxVM mirroring. Once the mirroring has completed we would break the mirror from the old LUNs and be running on the new storage.
The catch here is that the customer is not 100% sure they want to be on the new array and wants the ability to failback quickly if there are problems, such as performance. There are several terabytes of data so the original sync could be quite time consuming. If, for example, it takes 12 hours and the customer complains about the performance, we want to get back on the old disks as soon as possible, not after waiting another 12 hours.
In LVM, I could do this simply with the lvsplit and lvmerge commands. The lvsplit breaks the mirror into a new lvol and keeps a bitmap of all the changes so that resyncing the mirror happens much more quickly, very similarly to a snapshot. If, after a couple of days, the customer is satisfied, we would completely remove the old LUNs and be done with the project.
Can anyone help me with the commands to do the same in VxVM? I found conflicting answers on Google. One says an exact equivalent to lvsplit/merge is the command vxassist snapshot and vxassist snapback. Antother sites suggests using vxplex detach and vxplex attach. So if anyone has suggestions on the best way to accomplish this, I'd really appreciate it.
One thing I need an answer for, is where the bitmap is stored and how to make sure we do not fill it up and lose it. This is an active database so the delta might be quite large for all we know after a few days.