Some vendors offer, or will offer, both deduplication and compression. Others, such as Ocarina, decode already-compressed files before optimizing them. Randy Chalfant, vice president of strategy at Nexsan, argues that data should be compressed at the file or operating system level and deduplicated on the storage target. Cloud-based deduplication and compression vendor Asigra Inc. first compresses and then deduplicates data, and stores only changes made to it.
The choice of whether, when and in what order to use both compression and deduplication depends on factors such as whether compression will make it easier or harder for the deduplication software to scan for redundancies, what tier (primary vs. secondary) you're looking to optimize, and how quickly the product can return data to a usable form when needed.
-- Robert L. Scheier
Real-time compression that doesn't delay access or slow performance by requiring data to be decompressed before it's modified or read is suitable for online applications like databases and online transaction processing, says Schulz. The computing power within modern multicore processors also makes server-based compression an option for some environments, he adds.
Allen of i365 says the benefits of compression vary. It can reduce data by ratios of 6:1 or more for SQL databases, but for file servers the ratios are closer to 2:1. According to Fadi Albatal, vice president of marketing at FalconStor, compression is most effective on backup, secondary or tertiary storage, where it can reduce storage needs by ratios of 2:1 to 4:1 for "highly active" database or e-mail applications. When information management services firm Iron Mountain Inc. archives applications, compression and deduplication reduce storage by as much as 80%, says T.M. Ravi, Iron Mountain's chief marketing officer.
IBM focused attention on compression of primary storage with its acquisition of Storwize, whose appliance writes compressed files back to the NAS device on which they originated or to another tier of storage. Storwize is beta-testing a block-based appliance, says Doug Balog, vice president of IBM storage.