Platter capacities plateau

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Per-platter capacities for 3.5-inch disk drives hit the wall in 2003. Vendors expect to post incremental density gains going forward, until new technologies can reach the market.

Keeping track of disk technology used to be easy: Each year, you could count on capacities to go up, performance to improve and drives to become more reliable. But those metrics don't apply to what's happening today.

Manufacturers such as Hitachi Global Storage Technologies (HGST), Maxtor Corp., Seagate Technology and Western Digital Corp. no longer focus on doubling capacities or spinning platters at faster and faster rates. Instead, emerging products are being tailored to increasingly specific missions, from affordable ATA drives for nearline storage to compact form-factor designs for blade server environments. New lower-cost drives are ushering in new ways to do backups.

Storage managers should see an explosion of disk storage options, punctuated by four key trends in the next 12 to 18 months:

  1. Leveling off of capacity growth
  2. New serial-based drive interfaces
  3. Smaller form factor drives
  4. Increasing drive category crossover
The flattening capacity curve
In 2002, drive capacities hit the brakes. Capacity figures that once doubled every year are now expected to double only once every two or three years. (For another perspective on disk drives, see "Best Practices: Five axioms for storage") The culprit is the increasingly difficult challenges in boosting areal density. Currently, the largest ATA drives weigh in at 400GB--a figure that won't likely double before the end of 2006. In fact, the bump from 300GB to 400GB drives earlier this year was achieved not by increasing areal density, but by adding a fifth platter to the drive packaging.

Sharply higher capacities are emerging in SCSI and Fibre Channel drives, which traditionally have lagged well behind their ATA counterparts. New products such as Hitachi Global Storage Technologies' Ultrastar 10K300 and Fujitsu's MAT3300NC/NP offer peak capacities of 300GB--up from 146GB last year. Seagate is also expected to roll out high-capacity Fibre Channel disk drives. Initial product is expected to hit the streets in volume this summer and fall.

None of the vendors expects sales of so-called "fat fibre" drives to account for more than a small fraction of SCSI and Fibre Channel disk sales. One reason: Enormous drives can take several hours or even days to rebuild following a disk failure. That leaves a typical RAID array wide open to catastrophic data loss during the rebuild process. Network Appliance Inc. (NetApp) delivered a product earlier this year with its dual-parity (DP) architecture, which puts two dedicated parity drives behind the primary disk. But a DP-like product imposes costs that once again slant the argument in favor of less-spacious drives.

Massive drives can also limit the performance of storage arrays, which rely on parallel disk access to speed reads and writes. The new class of drives should find a ready home in direct-attached server storage, and may offer a good fit for Fibre Channel-aligned enterprises supporting less-critical backup and archive applications. For enterprise storage arrays, however, the capacity sweet spot will not likely shift out of the 73GB range, despite the arrival of jumbo 300GB Fibre Channel drives.

Recommendation: For non-critical, RAID-enabled environments, consider 300GB ATA drives--they offer excellent costs per gigabyte and acceptable reliability.

This was first published in June 2004

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