Looking for hard-disk performance and RAID security at tape prices and scalability? Well, that is what Copan Systems claims it can offer with its new Revolution 200T library.

The system is intended for enterprises backup and restore operations, and the storage of large scientific files. Scalable from 56TB to 224TB, it uses Serial ATA disks in a Power-Managed RAID design. There can be up to 896 drives in a single cabinet, using fourteen drives per 3.5TB "canister".

Power-Managed means that only disks needed to restore information or for writing are spun up. After use they spin down. The remaining disks are idle. This lowers electricity needs, both for turning the disk platters and for cooling the array. Less heat and vibration means the drives can be packed closer together, making the unit smaller - see Clariion comparison below.

The architecture uses a massive array of idle disks known by its pleasing acronym of MAID.

Even taking into account the spin-up time, the Revolution 200T disk library is said to deliver ten times the speed of a tape library. Spin-up time is estimated at ten seconds. Access time in a tape library is typically between 30 and 40 seconds, going up to 80 seconds according to Copan's CTO, Aloke Guha.

The 200T's array controller is simplified, compared to that of an array of constantly spinning drives, because I/O demands are smaller. It is also optimised for streaming large amounts of data rather than many, smaller random I/Os.

Powering down disks between periods of use increases their longevity, according to Copan, to SCSI disk levels. SATA drives generally can be spun up and down 40-50,000 times.

Copan says that current disk technology is three to five times more expensive than tape. If you have a 100TB archive then the raw costs are $300,000 for a tape library or a million dollars for disk. A 100TB Revolution 200T will cost around $350,000. This fills what Dave Davenport, Copan president and CEO, says is a "hole in the storage hierarchy".

According to the Yankee Group, a Clariion DL 700 costs about $14 per GB and holds up to 174TB. The Revolution 200T costs around $3.50 per GB - four times less - and holds up to 224TB, over three times more. A fully configured Revolution 200T will cost just over $780,000. For comparison indicative buy prices on Overland Storage tape libraries supporting up to 500 slots and 100TB of capacity native (200TB compressed) are $90,000 if configured with 2 LOT2 tape drives and approximately $180K if configured with 12 LTO2 drives.

Copan cites research by the Enterprise Storage Group which states that the biggest problems with current backup/recovery processes are that they both take too long and are too labour intensive. Disk-based backup has a higher success rate than tape, and the amount of data backed up to disk then to tape will increase by 12 percent over the next two years.

A tape library has an advantage in that tape catridges can be removed for off-site vaulting. Guha thinks that tape will remain the preferred choice for archive storage with disk being used increasingly for reference and fixed-content data needing to be online.

Tape libraries can also scale to far higher capacities than the Copan product can within its rack. For example, an ADIC Scalar 10000 tape library holds up to 789TB of raw data (LTO2). Compared to StorageTek's large Powderhorn libraries, the Copan unit is not even in the same capacity class.

Backup software
The Revolution 200T has a virtual tape library interface and will work with existing backup/restore software from Veritas, CommVault and Bakbone, but running on Solaris and Linux servers only. Expect wider server O/S support in a future release.

The Revolution 200T will be shippable in the US in the third quarter of this year. It should arrived in the UK by the end of 2005. There is more information about the device here.