Storage for your digital stuff has never been cheaper. We recently received an ad in our inbox from a well-known electronics retailer. The startling item in the ad was a 1 gigabyte compact flash card for under $90. Recently, Jim Louderback, in his
Mass storage today is cheap and plentiful. Despite this seeming cornucopia of buckets for your bits, storage technology is still evolving. We’ll take a look at some of the key areas of technical evolution in the arena of personal storage. Here, we’ll be focusing on disk-based media, both optical and hard disk, with an eye on near-term buying decisions. Note that we’re not going to discuss tape technology, as it’s no longer a common component of desktop PCs, even though it’s still heavily used in enterprise environments.
It’s About Connections
Connecting mass storage used to be simple. Attach the IDE cable, make sure the master/slave/CS jumper is set correctly, and go. If you were one of those rare users who used SCSI in a desktop PC, things were somewhat more complex, but you were also typically more technically savvy than the average user, or even the typical DIY user.
Today, connections are a bit more complex. Let’s take a look at the new methods for connecting storage before we dive too deeply into the actual storage technologies.
Let’s first turn to desktop hard drive connections. For years, the standard mass storage connection had been parallel ATA, also commonly referred to (somewhat incorrectly) as IDE. In the past couple of years, the industry has shifted gradually to Serial ATA. The original Serial ATA link, AKA Serial ATA 1.0 or SATA 150, offered a maximum transfer rate of 150 megabytes per second over a 1.5GHz serial link. SATA transfers 1 bit per clock, using 8b10b encoding. The encoding overhead is responsible for the maximum actual throughput of 150MB/sec instead of the theoretical link rate of 187MB/sec.
Serial ATA offers a point-to-point topology, which means one connector per device (as opposed to Parallel ATA’s two devices per connection). Since the connectors are so compact, it’s relatively easy to squeeze four connectors into the space of a single parallel connector.
In addition, SATA was designed from the outset to be scalable. While the current implementation tops out at 150MB/sec, the next version scales to 300MB/sec. The roadmap even allows for a 600MB/sec (6GHz) implementation.
However, you won’t have to wait for SATA-II’s 300MB/sec speed to get better performance. Chipset makers are implementing native command queuing (NCQ) for current generation SATA interfaces. So far, Maxtor and Seagate have announced support for Native Command Queuing in their latest lineup of SATA hard drives.
NCQ improves overall disk performance by allowing commands to stack up in the hard drive while the storage subsystem is waiting for things to happen. But NCQ is more than just a command buffer. It also incorporates a smart scheduling and instruction reordering capability, which understands issues of rotational and head latencies inherent to hard drives. This way, commands are issued more efficiently and executed in relation to current disk read/write head positioning (linear and angular). The result is better overall disk throughput. While enterprise-class SCSI drives have offered this capability in the past, this is the first time a desktop platform has natively integrated NCQ into the core logic.
Western Digital has yet to announce support for NCQ, but has implemented TCQ (tagged command queuing) in the company’s latest line of
Note that the average desktop user may not see big gains using command queuing, but anyone using applications that heavily access the disk may benefit.
The key word: denser.
Drive makers are busy packing more bits per square centimeter into each succeeding generation of hard drives. This has several impacts:
- Read performance speeds up, because the number of bits that pass under the read head increases as the platter density increases.
- Costs go down. A 100GB, single platter drive costs less than a two platter, 80GB drive, in general.
- New capabilities emerge. Hitachi is shipping 4GB Microdrives just 1 inch across. These are commonly found in digital music players and digital photography. Toshiba is readying a 0.85″ drive that holds a gigabyte.
Size and Speed Count
PC hard drives have pretty much been stuck at 7,200 RPM for the past few years, with some 5400 RPM budget drives still available. While Western Digital has tried to jump start the market for 10,000 RPM Serial ATA drives, those were more suited to server drives or configurations with RAID arrays.
In addition to data density, companies are experimenting with different platter sizes. The aforementioned Western Digital Raptor line spins at 10,000RPM, but makes use of a 3-inch (rather than 3.5-inch) diameter platter. Seagate is shipping its Savvio line of 2.5-inch, enterprise class drives that rotate at 10,000RPM. These currently support only SCSI or serial-attached SCSI, but there’s no reason the technology couldn’t eventually filter down to compact desktop systems.
Drive makers are also implementing larger buffers. Recent drives announced by Maxtor now implement 16MB buffers. As capacities grow larger, bigger caches are needed just to keep track of the tracks.
Personal RAID is becoming increasingly popular. We discussed the practicalities and pitfalls of
However, the benefits of RAID 0 are unclear. In theory, you’ll get larger drives and better throughput with a striped RAID 0 array. However, Storage Review, a well-regarded site focused on performance of data storage products, has suggested quite strongly that performance gains with RAID 0 arrays are minimal in typical desktop environments. Add in the potential for data loss, since you’ve doubled the point of failures by using two drives to emulate a single one, and the risks may not be worth the rather meager reward.
On the other hand, chipset makers and driver writers have also implemented RAID 1. One of our production systems has a physical second drive that’s really a pair of 250GB drives set up in a RAID 1 configuration. Most of our valuable data is stored on the redundant volume, giving us a bit more security. PCI add-in cards can implement RAID 5 and beyond, making data loss less likely, but they also increase the cost substantially. If you can get a pair of 160GB drives for under $100 each, building a 160GB redundant array suddenly seems affordable.
Core logic makers are expanding their capabilities to match or exceed that of the low-end add-in card makers. For example, Intel’s latest 9xx chipsets let you mix and match a RAID 0 and RAID 1 volume by using just two physical hard drives. Via will be integrating RAID 0+1 into their 8251 South Bridge, provided that additional SATA ports are also added to the system (which requires an additional “SATALite” chip). This means you can mirror a pair of striped arrays, which allows you to have the best of both worlds–data redundancy and faster throughput. But it’s also expensive, as you’ll need four drives.
As data storage gets cheaper and natively faster, the idea of redundancy to help protect your valuable data becomes much more compelling than the desire for slightly faster throughput. And RAID 0’s ability to give you gobs of data storage space is minimized somewhat as drive makers ship products that offer capacities in excess of 300GB. As more and more of our digital life gets stored on rotating magnetic media, preserving those bits becomes vastly more important than loading the next Doom 3 level two seconds faster.
External storage typically shows up in two varieties: The most common today connects via USB or FireWire to a single computer at a time. Less common among home users is network attached storage (NAS), but this type of storage is gaining traction, as home networks become more prevalent.
System Attached Storage
External hard drives are becoming quite common, both as adjuncts to system drives and as backup devices. Most external drives now ship with backup software and “one button” operation. This allows you to punch a button on the front panel of the drive to launch the backup software and automate the backup process.
Recently, Western Digital has added flash memory card readers to their external drives and begun calling them “media centers.” While that’s a bit of marketing-speak gone wild, it’s still a useful feature, though memory card readers are becoming increasingly ubiquitous.
Some of the second-tier manufacturers, such as LaCie are building external drives into enclosures that use FireWire 800 (aka 1394b). This doubles the potential throughput of 1394a, and is almost double the theoretical maximum transfer rate of USB 2.0. Of course, you’ll also need a FireWire 800 PCI card, unless you have one of the newer Apple systems.
Perhaps more interesting are the emerging class of external Serial ATA drive, such as the
A host of external enclosures are now available from a variety of online and retail sources, so you can build your own external drive. Want to use a 2.5-inch laptop drive, and suck power from the USB port? You can do that. Want to build a dual-purpose, FireWire 800 and USB 2.0 drive? You can do that, too.
NAS systems can take a variety of configurations, from the more traditional box that’s really a thinly disguised dedicated PC to an emerging class of solutions targeted specifically at home users. Combination devices are also hitting store shelves, which have additional capabilities like built-in routers and network switches.
The problem with many of the more-traditional NAS approaches? Cost. Spending in excess of $500 for a network-accessible, 120GB hard drive probably isn’t in the cards for most users. Setting up and connecting these drives is often a non-trivial process. Fortunately, some companies, such as Ximeta, have offered products substantially cheaper than business-focused NAS drives.
More interesting are products that specifically target home users. For example, the
While Mirra’s approach does make life simpler for neophyte users, more tech-savvy users may want something that’s easy to set up but offers a more traditional approach to network drive access. One interesting little product that shipped recently is the Linksys Network Storage Link. This small device attaches to your network and lets you attach external hard drives to a USB 2.0 port.
Out of the box, the Network Storage Link isn’t perfect. You have to format the drive with a proprietary format rather than FAT32 or NTFS. But it’s a convenient solution that allows users to be flexible about their external storage costs. The Linksys device also lets you connect to your files over the Internet, if you need that.
As happened with CD rewritable drives, DVD recorders have steadily improved in performance and come down in price. Unlike CD writers, though, DVD burners have recently increased in capacity by offering support for DVD-R DL (dual-layer). Usually, a new technology like DL means premium pricing, but that disappeared almost overnight, and we now have a host of dual-layer capable drives priced well under $100.
Surprisingly, single layer drives haven’t dropped all that much. For example, OEM Pioneer DVR-A07 drives (
Dual layer media is a different story entirely. DVD+R DL discs are still hard to find, and when you do find them, the prices are in excess of $10 per disc. You’d better really want to record a dual-layer DVD at those prices–and hope you don’t create a coaster. Meanwhile, single-layer disks often cost less than a buck a disk, even for rewritable blanks.
We’re expecting to see high-capacity optical drives using blue lasers by 2005. However, consumer blue-laser drives, which are likely to act as VCR replacements, might ship before the end of 2004.
When making the decision for buying storage for your desktop PC or home network, it’s worth taking a look at your needs:
- Do you have only one PC shared among family members?
- Do you have a home network?
- Is your network wired or wireless?
- Are you the “home sysadmin,” having to support family members’ PCs as well as your own?
- Do you have a need to get to your data from anywhere in the home?
- How important is data safety? If you’re just using a PC for casual games, reinstalling apps and the OS may be a nuisance, but if you’re running a small business, losing data would be a major disaster.
Buying or Upgrading Desktop Hard Drives
First, think about your system. If you’ve got an older system, you’ll probably still want to go with parallel ATA. The good news is that parallel ATA drives are getting cheaper by the day, as manufacturers shift to Serial ATA. But at some point, those prices will start to go up.
If you have systems with native support for Serial ATA, definitely go with SATA hard drives. Prices for SATA storage is much cheaper than it was a few months ago, and only slightly more expensive than parallel ATA drives. Already, drives with NCQ support are trickling into the retail channel. For example, a Seagate ST3160827AS drive, which supports NCQ, goes for around $105 list price. The ST3160023AS (
Note, however, that only the Intel ICH6R I/O controller hub currently supports NCQ, although Via’s 8251 will be shipping fairly soon.
What about RAID? Unless you really need the added throughput and capacity of RAID 0 (for example, heavy digital-video editing with uncompressed video), we suggest avoiding RAID 0 for normal desktop use. But it’s worth considering RAID 1, especially if you value data security. RAID 1 does not replace a good backup strategy, but does give some piece of mind if one spindle fails.
When should you consider buying an external hard drive?
If you have the need for portability, an external drive makes good sense. For example, you could back up all your digital music files to an external hard drive and have a portable music library. External drives also make backup easier–or at least faster–than tape-based solutions. But keep in mind that an external drive is still rotating magnetic media, so it can fail just like any other hard disk. Also, tape or removable cartridge drives let you store backups off-site. Of course, you could also consider DVD recorders for backup. Backing up to a few DVD+RW disks is a bit slow, but you can keep the discs off-site just as with tape.
Buying Optical Drives
The decision is easy: Get a dual-layer drive. Sure, media is pricey now, but that’s likely to decrease over time. The new DL drives are also speedy with single-layer media–as fast as 16x record speeds for DVD+R.
Note that most optical drives are still parallel ATA, though Plextor is shipping a version of the PX-712A (
Network Attached Storage
This is worth considering if you have multiple family members on a home LAN. If you tend to wander around the house with a wirelessly connected laptop, it’s even more useful. With Ximeta-class drives costing under $200, they’re not all that pricey. It’s still something of a niche solution, though.
Let’s say you were planning on upgrading your entire desktop storage subsystem? How much would that cost today? Let’s take a look:
|Primary hard drive (160GB SATA)
|Secondary hard drive: RAID 1 array (2x 160GB SATA)
|Dual-layer DVD recorder
|External 250GB for backup
This is a pretty premium setup, but you’re getting over half a terabyte of available storage, and redundancy for 160GB of your valuable data. If you’re on a tighter budget, consider this:
|2x 160GB SATA RAID 1 array
|Dual layer DVD recorder
That’s going to set you back less than $300. You’ll have redundant primary storage and the ability to back up to optical media.
As more and more bits become necessary for daily life and storage is cheaper than ever, it’s likely time to rethink your needs. While we believe that NAS is still a niche solution for home users, as our digital storage needs become increasingly distributed, the NAS drive may become the digital media hub of the future. If you’re still sitting there with a single, 40GB drive with all your data on it and one CD-RW optical drive for backup, it’s probably time to rethink your storage strategy.