Dataram finally launched their “mystery product”; it turns out I was on the right track with my predictions about this last month:
My best guess at this moment is that their new product will be a caching appliance that can be inserted transparently between a storage system and the clients; probably only for NAS devices at first, since I think that will be easier to implement. I’d also guess that the appliance and the included software will automatically detect data hotspots and cache only data that is accessed frequently.
The only bit I got wrong was the NAS part; instead, the product is meant for SANs. It’s called the XcelaSAN; the short summary is that it’s a 2U rack mount unit housing dual power supplies, a small UPS, SSDs for “durable” storage, and 128GB of RAM.
It’s placed between your SAN and the storage clients, using eight 4Gbit/s Fibre Channel ports. The cache works dynamically, but you can also specify LUNs to be cached manually. The chances of data loss are minimized by (amongst others) using ECC memory, Chipkill technology, built-in redundant components, and SSDs for storing the data in case of a power failure. For maximum protection you can even install two XselaSANs in a fail-over pair.
The only thing that struck me as slightly strange was this statement:
“XcelaSAN’s write-through mode ensures that all data on an assigned LUN is written to the attached disk array’s write cache prior to notifying the server that the write is complete. This mode assures both high performance and data protection for mission-critical data.”
I’d love to see some benchmarks when using write-through mode; I don’t see how this will offer better performance than just relying on the SAN controller’s write cache and the read cache on the client side. Dataram is offering a 30-day evaluation period, so if you think your SAN might benefit from more cache you might want to give it a try and see whether it does offer the “up to 30x performance improvement” mentioned by Dataram. If you decide to keep it, pricing starts at $65,000.
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[...] NAS and SAN systems has been a hot topic the last few days. Late last month Dataram presented their XcelaSAN appliance that sits between a Fibre Channel SAN and the clients accessing it, storing data in RAM. A couple [...]