I have used svnsync and it took a while for rev 120 but it went successfully. There is no space constraint but it was taking the longer time when compared to other repositories. So for now, i have migrated most repositories and will see how i am going to migrate the rest in coming months. rsync is not useful for me since I am moving from one to another server without altering the existing setup.
For -M options - is this is the cache for processing for dump files. do I need to increase the value in MB like -M 1024 to speed up.
Sorry for late reply.