Hello, again,
Let me rephrase :-). Both devices are in general used to perform replication to an identical device. Using a Centera has benefits where the EV Centera API informs EV items are secure. Isilon does not have that. (I know, we're in testing phase). The Isilon in DC1 is replicated to an Isilon in DC2. This replication is fast, and (so I am told) secure. Having to backup TB's of data, where you know the data is replicated, is (sometimes) overkill.
I 'solved' it by setting the Vault Store (and it's partitions) that use Isilon in backup mode, write a triggerfile (IgnoreArchiveBitTrigger.txt), then take the VS out of backup mode. EV will then consider all files created before the date/time of the triggerfile as secure, and update the databases accordingly.
If your backup is slow, it might have several reason. You should involve your backup solution vendor, and perhaps EMC, to assist you with that.
Does that better clarify?