Having the server do a copy of one LUN to another LUN is certainly an option, however it will force you to be aware that the data must not be corrupted during the transfer. For example, if all the 500GB are in files, then just make sure that your copy algorithm knows to retry files that are open. If it’s a database, put the database in hot backup mode. Note: this may cause some disruptions to whatever application you have running on this data. Also, if the 500GB is being used by several servers, you may have to disconnect all servers other than the one you’re using to copy the data. It’s not suggested to allow two servers to see the same LUN even if one is just copying it unless you have very specific instructions from your copying software.
If both SANs are of the same model and are licensed for “replication”, then you can use the replication feature to copy the data, usually with less impact to your running applications.