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Storage: Better Technology, More Choices

Jan 31, 2006 2:10 PM, Dan Ochiva

While new HD camcorders and all-in-one production suites have been garnering the news of late, there’s plenty of churn and innovation in storage devices and technologies.

Granted, the technology isn’t as sexy perhaps. But you’ll be using the breakthrough gear to edit, playout, and archive your work for years beyond that last camcorder or software purchase.

Some of those breakthroughs come after years of R&D.

Case in point: Perpendicular recording is coming to a drive near you. What’s that? Well, up until now, hard drives have only laid down their bits of data in longitudinal tracks: short magnetic structures that are laid flat, head to toe, on the disk’s concentric tracks.

Now, engineers have figured out how to store that same data in individual data structures that record into the depth of the drive’s surface, standing the data bits on end. That way, many more bits can fit into each concentric track.

Earlier this month at CES, Seagate claimed title for delivering the first notebook PC disk drive built on perpendicular recording technology. It’s Momentus 5400.3 2.5-in. drive fits more data on the same size drive platter (a new record of 132 Gbits per square in. says Seagate).

With the new drive, performance specs improve without increasing spin speed too. Since the new data orientation allows more bits to pass under the drive head in the same amount of time, you get a ‘free’ speed boost. Other benefits accrue: there are no increases in power consumption or heat generation, with even drive reliability improving (the technology enhances data resistance to thermal decay).

But it’s not just new disk technology that you need to be up on. Connections count – you have to be as up to date on interface developments.

After all, it’s how you integrate your new drives and storage with the rest of the production process that will allow you to reap the benefits, or not. Picking the wrong drive interface can reduce overall performance.

By learning a bit about what goes into each standard, you’ll be better informed when it comes time to decipher ads or ponder a purchase.

Today, staying on top of drive development means knowing about the major drive I/O interfaces: Fibre Channel (FC), ATA, Serial ATA (SATA), and SCSI. Meanwhile, Serial Attached SCSI (SAS) is another potentially important, but still nascent standard.

Some vendors also tout iSCSI (Internet small computer system interface). This IP-based standard links data storage devices over a network, transferring data by carrying SCSI commands within an IP wrapper.

Today’s major trend? Moving away from the parallel connection storage technology that’s been the standard from the very beginnings of both large scale and personal computing.

You’ll still find the vast majority of laptops and desktops using Parallel ATA (PATA) interfaces. Many new workstations now feature SATA (Serial ATA) drives, and they’re starting to replace PATA in server and external storage.

These new serial interfaces support faster transfer rates, reduce the size and complexity of cables and connectors, and provide solutions to low-level problems such as signal skew, crosstalk, and limited device addressability.

While SATA drives bring new technology to a lower entry level tab, if you need rock-solid enterprise level systems, you’ll have to be prepared to spend a little more.

“Enterprise” SATA drives are built to the same tough mechanical specs as those for SCSI, Fibre Channel, and SAS. Enterprise SATA drives. All have comparable MTBF (mean time between failure) ratings at high duty cycles and include server-level capabilities including queuing (the hard drive is ‘smart’ enough to re-order the many read or write demands it gets from the computer, which it then writes to the closest disk sectors, rather than hopping around with each new command); dual-port capability (also known as SATA Port Selector, each drive can host two connections, which enables external storage arrays with two controllers to both connect to each hard drive. If one controller fails, the other controller will continue to operate).

For many years, SCSI-connected drives ruled at the top. It was the first widely deployed interface to answer the need for ultimate speed demanded by graphics and effects workstations.

The “latest” version of SCSI is Ultra320 SCSI, which has actually been around for the past two decades. However, many technologies consider Ultra320 SCSI the end of the line for parallel SCSI technology. For a number of technical reasons, it would be very difficult to pull off an “Ultra640” SCSI.

SCSI standards groups, however, have created a replacement connection for parallel SCSI -- Serial Attached SCSI (SAS). Don’t confuse this with iSCSI, which uses the Internet Protocol. SAS gains more throughput and reliability by using a direct connect technology, not IP’s packet switching. Another advantage of SAS systems is that they can accept both SAS and SATA drives; this helps deliver a more diverse set of storage configurations and price points.

Fibre Channel (FC) hard drives and FC storage systems, another serial connect technology, still retain their title as the most specified drive technology for high-end networked storage. The technology has moved beyond its introductory versions, which caused much hair pulling due to inconsistent standards implementation by vendors.

Among the numerous charms of Fibre Channel are its throughput rate of 4 Gbps, dual porting, and a hot-pluggable interface (drives can be installed or removed while the host system runs). FC also allows extremely long cable runs between drives and hosts (up to nearly 10km when using fiber-optic connections).

If you need that speed yet still want to save some money, keep your eye on an interesting new development: the FC-SATA spec. Advanced by gear maker Emulex, the standard expands FC capabilities to include compatibility with less expensive SATA disk drives.

SAS, the successor to parallel SCSI, builds on its best parts – such as reliability, scalability, and interoperability—while offering improved bandwidth and performance. Like SCSI, SAS drives are fast, much faster than standard SATA for example, with speeds of some 15,000rpm. SAS currently delivers a maximum data-transfer rate of 3Gbps, with a road map to 12Gbps.

One emerging trend, although mainly in the enterprise markets at the present, is the deployment of SAS and SATA drives together in tiered storage systems, since the drives are connection and interface interoperable. Tiered systems usually employ faster SAS drives for online or nearline storage, while the system transfers older files to archives on the less expensive, less bulletproof SATA drives.

If you decide to go with SATA drives for more crucial nearline storage, some knowledgeable types suggest that users should look for drive technology that ensures drive performance in high rotational vibration environments, such as the when many multiple drives are used a single enclosure.

Other suggested “good practices” features are native command queuing (NCQ enhances performance) and staggered spin-up (this enables the host to individually turn on drives in multi-drive configurations.) This reduces the power drawn when a system boots, allowing for smaller power supplies. Drives can also be spun down to save on wear and tear as well as power needs.

Whatever choice you end up making, remember to look at the long term viability of these interface formats before you sign that check.

© 2008 Penton Media, Inc.