Adaptec beefs up cache protection in Raid adapters

Adaptec's Series 5 Raid adapters use Flash-based backup of the cache memory

Adaptec has enhanced its Series 5 range of high-performance Raid adapters with Flash-based backup of the cache memory. Unlike battery backup, this feature provides increased reliability with no maintenance required, according to the firm.

Available to order immediately, the new Series 5Z consists of three models that complement the existing range of adapters for Serial ATA (Sata) and Serial attached SCSI (SAS) arrays, but adds a zero-maintenance cache protection (ZemCap) module that stores all data from the controller's cache memory in the event of a power failure.

While the current 5 Series adapters have battery backup to preserve cache contents for up to 72 hours, the ZemCap copies the data from cache into 4GB of Flash memory capable of preserving it almost indefinitely.

Adaptec's EMEA marketing manager, Juergen Frick, explained that there has been increasing uptake of Raid caches with battery protection over the past few years.

"There are various reasons why a cache is used to accelerate the performance of Raid arrays, but you must protect the cache - even if the power fails - or data will be lost," he said.

Caching hides the fact that Raid level 5 or 6 writes actually require multiple writes across the disk array to complete, Frick explained. Using a cache also enables drives to spin down and save energy during periods of minimal activity by serving requests out of the cache.

The drawback to batteries is that they can take several hours to charge, during which time the system could be vulnerable to failure. Batteries also degrade over time, so manufacturers recommend replacement every one or two years, which means opening up servers and workstations.

Frick said that new Series 5Z adapters are effectively zero maintenance, as the module should not need replacing. A high-density capacitor provides enough power to back up the adapter cache if the power fails, and this takes just minutes to charge from power on.

Like the Existing Series 5 cards, the new models have 512MB cache and use Adaptec's Unified Serial architecture that can support Sata or SAS drives, or even a combination of the two.

The three cards consist of the 5405Z with four internal ports, the 5805Z with eight internal ports and the 5445Z with four internal and four external ports. Prices are expected to be $785 (£480), $965 (£590) and $1,045 (£639) respectively.

The new cards have the same 1.2GHz Intel XScale processor, and support 3Gbit/s SAS. However, Frick said that Adaptec is currently in the process of producing its own ASIC that will enable a successor card due next year to support 6Gbit/s SAS.

"We will not be the first to 6Gbit/s, but we believe our architecture will be completely different from what is on existing controller cards," he said.