Build It: External USB 2.0 Hard Drive

 
 
By Loyd Case  |  Posted 2003-01-16
 
 
 

Build It: External USB 2.0 Hard Drive


 

The Conundrum of Big


Storage"> My system has 240GB on it -- two 120GB physical drives. I say that, not to brag -- I know quite a few people with even more storage -- but because having that much storage creates a major headache: backups. Backing up to CD-RW or even DVD rewritables isnt really an option, except for spot backups of critical documents.

Multiple PCs – which more and more homes now have -- create even more problems.. And if youre deep into digital media, youll find that moving high-quality video and audio files from computer to computer can also clog up your network. Sure, you can always backup or transfer files over a network, but these file transfers can clog the net at inconvenient times. If you have a high capacity, portable drive, then you can perform multiple backups. Its the return of the sneaker-net!

The potential downside of using a hard disk for backup purposes is drive reliability. As we noted in our roundup of big drives, warranties for standard ATA drives – used by most USB enclosures -- have been reduced to one year, while the "special edition" drives are still at three years.

However, since were talking about using an external drive as a backup system or secondary storage, its unlikely to be up and running as much as the primary drive inside your PC. If youre really worried, Maxtor manufactures a line of ATA drives specifically for secondary storage -- these drives come with a MTTF (mean time to failure) in excess of one million hours.

This article is broken up into three sections. In the first section, we review external drive options, and discuss why we opted for USB 2.0. In the second, we review our selected drive enclosure, the Belkin Hi-Speed USB 2.0 External Drive Enclosure Kit (FSU209), focusing on drive installation, system setup and performance. Finally we wrap up this story with some conclusions and final thoughts on external drives.

Read it sequentially for all the details, or skip around, using either the table of contents below or the in-place links above, to get right to the information you need.

External Drive Options


Several external drive options exist at different levels of performance, capacity, and redundancy. One of the oldest types of externally attached subsystems used SCSI drives. Outboard SCSI RAID arrays are still used for certain mission-critical applications mostly in businesses. The SAN, or storage area network, offers another enterprise-class external storage solution. While personal SANs may someday make it into our homes, for now SANs are still considered high-end and beyond the scope of this piece, which focuses on personal external storage.

A few external IDE storage products have also been on the market, but havent been completely satisfactory. They have been, for the most part, not hot swappable, so you typically had to power down to swap out a drive. And you were still limited by the number of free IDE ports on a system. The most common variant has been drive bays that slide into the PC case and plug into an internal connector.

IDEs short cable length (24 inches, tops) has been the major limiting factor for IDE-based external drives. However, as Serial ATA begins to take off, well see more external drives, because the maximum cable length has increased to 1 meter.

After FireWire arrived on the scene, FireWire external hard drives used as backup or secondary storage became a familiar item, especially in Macintosh shops. On the PC side, IEEE1394 was less prevalent, as the standard has only recently become popular in most PCs and motherboards. Now that PCI firewire cards cost less than $15, these offer another viable option. But USB 2.0 is a standard feature on all current generation motherboards, so it obviates the need to install a PCI card.

Finally, a few external drives existed for USB 1.1 connections, but the maximum transfer rate of 12 megabits per second was too limiting for serious data transfer.

Once USB 2.0 hit the streets, USB became an interesting option. Weve seen a number of external CD and DVD recordable drives support USB 2.0. We reviewed several examples of these back in August. External hard drives have been somewhat slower in coming, but now theyre arriving in force, and most of the major hard drive suppliers now sell external drives supporting either FireWire or USB 2.0 -- or both.

While buying a drive thats already integrated in an enclosure has its appeal, you can also build one yourself. That way, you can choose the capacity and performance you need.

Unlike SCSI, however, external USB and FireWire drives wont match the performance of an internal drive. A SCSI drive is a SCSI drive, whether its external or internal. However ATA drives today all support high speed DMA transfers, while USB and FireWire do not.

Because of this, you might conceivably see performance differences that depend on the speed of the host CPU. Since you typically wont be using an external drive as primary storage, the differences shouldnt matter. What it does mean, however, is that you can get away without using the fastest possible ATA drive.

We deliberately chose a newer drive, the 7200rpm Seagate Barracuda ATA V, which we reviewed in our big drive feature. It wasnt the fastest in our roundup, but if we hit any performance limitations in USB 2.0, it should show up on this drive -- and we also get to toss in a comparison with our recent Serial ATA test. We chose to use a USB 2.0 external drive enclosure kit from Belkin.

The Enclosure


Product: Belkin Hi-Speed USB 2.0 External Drive Enclosure Kit (FSU209)
Web Site: www.belkin.com
Pro: Easy installation and assembly; quiet fan
Con: Pricey; USB 2.0 only (no FireWire support); limited to 137GB
Score:
Street Price: $109 list, $80 street (check prices)

Belkin supplied us with one of their new USB 2.0 external drive enclosures. This particular enclosure supports 5.25-inch devices, but has mount points for 3.5-inch drives as well. You can install either a hard drive or an optical drive in this case. However, there is no bezel for 3.5-inch removable devices, so you cant install a SuperDrive high capacity floppy or Iomega Zip drive.

One of the niftiest features of the Belkin enclosure is its relative lack of screws. The only screws supplied are to fasten the storage device to the case. The case itself snaps together, and the two halves are held in place by external bezels.

Inside the case are pre-connected ATA, power, and audio cables. The audio cable is used if youre installing a CD or DVD drive; there is no provision for digital optical output. A 40W power supply, the logic board, and a small cooling fan occupy the back portion of the case. The front bezel snaps in after the unit is assembled, or is left off entirely if you install an optical drive.

Drive Installation


The small manual -- more a pamphlet -- has all the salient details you need to know to install the drive. One issue thats not mentioned in either the manual or the Belkin web site is that the drive is apparently limited to 137GB -- the logic board no doubt has its own BIOS, and Belkin hasnt implemented 48-bit logical block addressing (LBA) yet. If you try to use a drive larger than 137GB, you will likely encounter errors. We first tried a 200GB drive, but couldnt format any size above 132GB. Then we dropped in a 200GB drive that had been formatted as an ATA drive. At first, it seemed to work, but we encountered sector read errors when the innermost tracks were being accessed. While its true that hard drives in excess of 137GB have been pretty rare until recently, were still disappointed that the drive enclosure apparently lacks support for 48-bit LBA.

Installing the drive is incredibly easy. All hard drives have four small screws on the bottom, in addition to the traditional screws on the sides. These bottom mount points are the ones you use for attaching the drive.

One other issue you need to be careful about is the master/slave setting. According to the manual and a warning sticker inside the case, the drive must be set to master. If its a Western Digital drive, make sure you set it to "master/no slave".

All you need to do is connect the IDE and power cable, attach four screws through the bottom of the case, and connect the top half to the bottom half. The side bezels snap on, and youre done.

One of the aspects of this enclosure we appreciated is the noise -- or lack of it. Weve seen external enclosures with fans that sound vaguely like a loud vacuum cleaner. Once completed, the enclosure (with its fan and internal drive) is quieter than typical PC case noise, so you cant really hear it. Even in a quiet room, its pretty quiet. The most significant omission in this case is the lack of a FireWire connector, but USB 2.0 is plenty speedy.

Setup Issues


We mentioned the problem with large capacity hard drives. Another issue is simply the finicky nature of Windows support for external drives. This is true with both USB and FireWire devices. Windows XP with service pack 1 installed, offers the best support, cleaning up some bugs that existed in pre-SP1 Windows XP. If youre running Windows 98/98SE/ME, youll need to install some updated USB filter drivers, included on a CD with the Belkin enclosure. Also included is a tray utility for managing external drives, but we found it somewhat superfluous.

Linux also has support for USB storage devices. More information on Linux support for USB is here.

Dont forget to heed the warning about setting the drive to master before installing. We left a drive at the slave setting to see what would happen. What happens is that you get an indication that a USB device is present -- but the drive never appears, either in the My Computer window or in the Windows Disk Manager. Its actually worse than if nothing happens at all. If you want to avoid this type of frustration, then make sure the jumper is correctly set.

Youll also want to be sure to plug it into a USB 2.0 port, if one is available. We have several systems that support both USB 2.0 and 1.1. Plugging the drive into a USB 1.1 port elicited a warning about potential performance issues. Thats certainly better than if the system simply allowed it to work, and then saddled you with less-than-adequate throughput.

Performance


We attached the drive to the same 2.8GHz Pentium 4 system weve been using for all our recent storage reviews.

Component Intel D845PEBT2 System (DDR333) Check Prices
CPU 2.8GHz Pentium 4 (533MHz FSB) check prices
Motherboard and Chipset Intel D845PEBT2, Intel 845PE chipset check prices
Memory 512MB Corsair XMS3200 DDR memory (run at DDR333, CAS2, "aggressive" timings) check prices
Graphics Nvidia GeForce4 Ti 4600 (30.82 driver) check prices
DVD-ROM Toshiba SD-1502 check prices
Audio Sound Blaster Audigy Gamer check prices
Ethernet Intel Integrated
Operating System Windows XP Professional, Service Pack 1 installed check prices

Our testing for the USB device only encompassed Winbench 99 2.0 disk tests. We didnt run the applications level benchmarks (Business Winstone 2002 and Multimedia Content Creation Winstone 2003), because it would be very unlikely that anyone would use a USB external drive for running applications.

Transfer Rate Tests
These charts really say it all.

Barracuda V ATA Transfer Rate Chart

Barracuda Serial ATA Transfer Rate Chart

Barracuda ATA in USB enclosure Transfer Rate Chart

The Serial ATA and parallel ATA results roughly follow the same curve. Since both the S-ATA and ATA100 drives support DMA transfers, you get the maximum transfer rate at the outer tracks with their higher sector density, trailing off steadily as the head moves through the inner tracks.

The USB drive behave differently, because the transfer rate caps out at about 30MB/sec (240Mbits/sec or about ½ the theoretical maximum speed of 480Mbits/sec for USB 2.0). Thats not slow by any means, but its not the 40MB/sec that the Barracuda can normally pump out over faster connections. If you recall our roundup of large drives, the Barracuda ATA has one of the lower maximum transfer rates around. But you dont get full benefit from very high transfer rates with a USB 2.0 interface.

Here are the charts of actual recorded maximum and minimum transfer rates.

As you can see, the USB 2.0 drives transfer rate at the beginning tracks is quite a bit slower than the other devices, while being nearly identical at the end.

CPU Utilization


Whats probably at issue here is the CPU utilization. Heres the relevant chart of CPU utilization.

The USB drive posts a whopping 66.6% CPU utilization -- higher is definitely not better here, folks.

If you think about it, 480 megabits/sec -- the theoretical maximum for USB 2.0 -- is around 60 megabytes per second. Even if you postulate a 20% overhead for encoding, then you still should see around 48MB/sec, assuming no other activity on the USB port. However, the lack of DMA necessarily means the CPU gets heavily involved in data transfers -- which will translate to a lower maximum transfer rate.

Note that this CPU utilization is measured during a situation where the drive is blasting the maximum amount of data across the bus (high-speed sequential reads). In situations where you might be reading and writing from the drive in more random patterns, you probably wont notice such a severe CPU hit.

Conclusions


You probably wouldnt want to try to use this drive as a primary drive, but as a secondary storage device, 30MB/sec is pretty darned good. With a 120GB capacity, plus the compression that exists in most backup applications, you can save a considerable amount of data to the drive.

Another potential application is expandable storage for media files. Why store all those MP3 files on your desktop system? Put them on an external drive, and you can take your music catalog with you.

If you opt to buy an off-the-shelf solution versus building your own, assuming you shop carefully, a 120GB drive plus the enclosure will set you back about $240 for a brand-name external drive manufactured by Maxtor or Western Digital. The Maxtor 5000DV (check prices), which is rated at 1 million hours MTTF, supports FireWire as well as USB 2.0. With the Western Digital, you have to choose between USB 2.0 and FireWire. Finally, both companies offer higher capacity drives -- up to 250GB in Maxtors case.

A host of white box shops will sell you drives in USB 2.0 enclosures -- and in some cases, dual-interface cases -- and only charge around $165-200 for a 120GB drive plus enclosure-- but these enclosures are often not as convenient as the $80 (street) Belkin chassis.

The fit and finish are often less polished, and assembling the case can be a real chore. Power supplies are often substantially noisier. On the other hand, you can buy them pre-assembled, so that may be a minor issue.

If you do-it-yourself, in this particular case (no pun intended), it may be worthwhile to shop around and buy a solution instead. The best pricing for a 120GB 7200rpm drive with a 2MB buffer hovers around $135 . Of course, thats not as much fun. But then, building a secondary storage device may not be your idea of fun anyway.

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