ExaGrid's been getting pretty good traction with its deduplicating NAS appliances for backup, with more than 200 customers. I wrote about ExaGrid's appliances just last month here. This week it's introducing a gateway model that lets you use iSCSI storage for your deduplicated data rather than buying an appliance with built-in storage. ExaGrid's tested the gateway with EqualLogic's iSCSI arrays and is pitching the combination as the best of both worlds.Like the rest of ExaGrid's line, you can combine multiple gateways into a single management unit and you can replicate deduplicated data between gateways and appliances. ExaGrid uses content-aware deduping, so it's a dedicated backup device. While they post process to dedupe data, the process runs asynchronously with backups so replication can begin soon after the backup job starts.

While I've been a fan of EqualLogic's arrays since I tested them four years ago for Network Computing magazine, of blessed memory, and I like the flexibility and scalability that a deduping gateway for SAN storage brings to backup, the combination seems like overkill to me. After all, one of the best things about EqualLogic's product is that it includes enterprise features such as snapshots, thin provisioning, and replication without charging extra every time you turn around, like NetApp or EMC.

But an EqualLogic PS5000E isn't cheap. A 4 TB (Raw), 3 TB usable unit is about $30,000 -- add in the $39,700 ExaGrid gateway and we're pushing $70,000 vs. under $40,000 for the EX3000 3 TB appliance. Before you start thinking about building the dedupe NAS that will eat Philadelphia, note that the ExaGrid Gateway is limited to 5 TB of disk space.

Now if I could back it up with a couple of Infortrend arrays ($10,000 for 12 TB usable), that would be cost effective.

Oh, and children -- setting up a SAN where both your data and backup are on the same array is BAD.