On Jun 16, 2011, at 2:49 PM, Tim Brown wrote: > Any one use emc's data domain devices for storage pools and replication > > Would like to here positive and negative issues.
My current employer has dozens of DataDomain DD690s and DD880s, all arranged in pairs in which one is primary and one is a DR replication target. (Each of our data centers is primary for some stuff and the DR site for other stuff, so there's no clear "DR site" vs. "main site.") We mostly use them as VTLs; it was an easier conversion that way than to overcome the resident anti-NFS bias and convert to FILE class devices while doing a migration to new hardware. We like them. We keep them relatively small for each head unit (20-30 effective TB, well below maximum capacities), so our cost per GB might be a bit higher than it has to be, but it saves us from having nightmares about DR scenarios when everyone wants to do restores at once and it all grinds down. (Only two FBA adapters? Compared to EMC's older CDL's, that's distinctly smaller.) We're just now converting from sometimes very large replication pools of "tapes" to replicate into several smaller pools of tapes to restore. We found out the hard way that when our WAN providers have bad days or when our long-haul switches start dropping packets, the restoration (and catch up) of the replication can be painfully slow when service is restored if you only have a couple of pools of volumes. Replication gets bound by housekeeping, not network bandwidth, if you have too few pools. Probably like any VTL technology, tape errors are almost completely a thing of the past. Capacity planning is a bit tricky; some workloads dedupe nicely, but some of our DDRs have dedupe ratios of 5 or less, We need to do a bake-off -- or study someone else's -- between using deduplication in a DataDomain box and using both client-side deduplication and server-side deduplication in TSM V6 and then writing to relatively inexpensive, relatively simple (but replicating) storage arrays. However, we keep pushing the limits of stability with our TSM V6 servers, so we haven't dared tried such a back-off yet. Nick
