What specs should I look for in an external hard drive

July 15, 2005 12:42 PM

I've just been given the task of buying an external hard drive for my work, and am looking for advice on which specifications I should pay attention to when comparing different options. The drive will contain data files, and the idea is that we'll run statistical analyses (using SPSS, SAS, R, etc.) on files that reside on the drive. The main feature I'm concerned about is speed -- I don't want the drive to slow down the analyses. But we won't be transferring large files to/from the drive very often, so transfer speed isn't important in that sense. Which features are most important for this purpose?

The physical size of the drive is important, because it will need to be stored in a small safe when not in use. So I was thinking a 2.5" form factor would be nice. But do I need to worry about such things as RPM, seek speed, cache, firewire vs. USB connection? Is there maybe a site out there that explains the practical implications of these various specs?

posted by nixxon to computers & internet (17 comments total)

Do not buy an external hard drive.

Buy an internal hard drive that meets your needs, and then buy an external enclosure in which to store the hard drive.

For USB vs Firewire, this will be largely determined by what your PC supports. If your PC supports both, it's really a tossup. That enclosure I linked to above comes in Firewire, USB, and Firewire+USB models.

As for everything else, StorageReview.com covers a lot of those issues. But for something like statistical analysis, the speed of the drive I linked will be more than sufficient.
posted by Jairus at 1:02 PM on July 15, 2005

I don't know about your application, but for mine (backups) I really hate the 3.5" drive I put together with a Nexstar kit. The problem is that USB isn't powerful enough to spin the drive, so I have to have a power adapter, too. Smaller external drives seem not to have that problem.
posted by Nelson at 1:44 PM on July 15, 2005

Jairus - could you please provide a little more information about why internal is superior to external? I'm not challenging you, I would really like to know. Thanks.

On preview, that NexStar enclosure is very, um, sexy.
posted by matildaben at 1:49 PM on July 15, 2005

Be warned that laptop drives are significantly less reliable than their desktop relatives.
posted by Mitheral at 1:50 PM on July 15, 2005

There's no difference between an internal drive in an external enclosure (purchased separately) and an external drive. One is preassembled, and probably comes with a warranty for the whole unit, and may be a little more expensive. That's it.

If you're really concerned about speed, don't buy an external drive. Buy a hot-swappable drive bay that allows you to connect a drive to the internal (SCSI or ATA) bus, and use that. It'll be boatloads faster. You may have to buy an internal PCI-ATA or PCI-SATA expansion card if you are already using both internal controllers, but they cost about $20 now.

The only drawback is that although the bays are marketed as being hot-swappable, you really can't pull or insert the drive while the system is running -- you have to shut down first. It just means you don't have to open the case.
posted by 5MeoCMP at 2:24 PM on July 15, 2005

I'll second Jarius -- I've got 2 vanilla EIDE drives (120 & 250 gb, 7200 rpm) spinning happily in ~$35 firewire enclosures (ByteCC ME-720) on my G5 Mac. The case measures 8.5 x 5.5 x 1.5 inches.

Also have a client using 2 x 120GB drives in external enclosures for backups -- put the current set on drive1, take it home & bring in drive 2. Repeat.

Nelson, if you wanted something that would not require a power brick, you'd need to go to an enclosure with a laptop drive in it, such as a VST Firewire drive. I'd probably buy one of those assembled, rather than get the case & drive separately. But you will pay more.
posted by omnidrew at 2:40 PM on July 15, 2005

3.5 drives require 12v and are too much for USB voltage. 2.5 drives are for laptops primarily and only require 5v, so you can get enclosures that require no additional power.

While they're great for transportability I wouldn't use one for constant access. They're often only 5400 rpm and probably not as quick as an external 3.5 will be. The enclosures are also more fragile and I have never seen one that was both USB and Firewire.
posted by phearlez at 3:06 PM on July 15, 2005

Some info about Firewire and USB, including speeds. And LaCie makes a USB/Firewire drive.
posted by SteveInMaine at 3:53 PM on July 15, 2005

There are lots of USB+Firewire enclosures, yes, but for 3.5" drives (like the LaCie you linked to). The question is, are there any laptop drive (2.5") enclosures that have both interfaces?

Also: Don't buy anything from LaCie. They have a horrible reputation for unreliable products.
posted by xil at 4:07 PM on July 15, 2005

Ditto on the LaCie non-recommendation. After years of avoiding their products, I just bought a 1TB ethernet disk NAS unit from them because it was a cheap solution to a simple problem, or so I thought. It just came back from LaCie after a nightmare couple of weeks in which I wasted hours recreating shares, reformatting the drive, etc. And getting through to their customer service was impossible for days. I ended up returning it for repair, but the time I've wasted with this was worth the difference for a better NAS unit.

No one seems to have mentioned that 2.5 inch (laptop) drives almost all run at 5400rpm or slower, whereas 3.5" drives run at 7200rpm. Given your need for speed, and the other drawbacks of a 2.5" drive, I'd say the hot swap bay with a 3.5" standard ATA drive is a far better solution. Granite Digital makes a really nice dual-bay hot swap firewire enclosure. Even if fast transfers aren't your premium need, you need fast seek and access times to run those stat analyses fast. I'm sure the bare 3.5" drive will fit in most safes. But the real kicker is -- I sure hope you plan to buy TWO (or more) of these drives, since if the data is important enough to store in a safe, it's important enough to keep backed up properly. And it's worth it to buy a premium drive from one of the top manufacturers (Western Digital has been my preference for reliability lately).

As for USB? Just say no. If you really want speed, and your machine supports it, and you can't use an internal ATA or SCSI bus, then another option is Firewire 800. But for practical purposes, Firewire 400 should be fine.
posted by realcountrymusic at 9:22 PM on July 15, 2005

If you want speed, I agree with everyone about getting 3.5" hd. Much much faster than a 2.5". If the safe is big enough, and you have the budget, consider getting either two hd's or a raid enclosure so you can have an instant backup (raid level 1). Stay far far away from Western Digital drives. There's a reason they tend to be the cheapest compared to other brands. Lousy reliability. Personally I've had good experiences with Seagate and Maxtor.
posted by edjusted at 9:54 PM on July 15, 2005

If you get an enclosure for a 3.5" drive, be sure to get one with an Oxford 911 or 922 chipset. They're the best in the field. The 922 suports both USB 2.0 and Firewire. Firewire is considerably faster and more robust, but many windows PCs lack a Firewire port. Firewire 800 is even faster, but doesn't help a whole lot if there's only one hard drive attached to it.
posted by blasdelf at 10:12 PM on July 15, 2005

xil asked:

The question is, are there any laptop drive (2.5") enclosures that have both interfaces?

Yes.

This is a great enclosure. When I upgraded my Powerbook's drive to 100GB, I pulled the 60GB and put it in this enclosure. It can be powered by the Firewire interface, the USB interface, and also has cables for interface and power for just about any combination (USB data and USB power if you have anemic USB power, 4-6 pin firewire and USB power if you have only 4-pin firewire, USB power/data, 6-6 pin Firewire, and it came with a power brick too!)
posted by tomierna at 5:39 AM on July 16, 2005

If you end up going the build-your-own external drive route, I highly recommend the Orange Micro Enclosure.

Between the fast USB 2 and Firewire 800 interfaces, the rugged case, and the fan (which others seem to lack*), the bells and whistles justify the extra cost, IMO.

I've bought four of them.

*there's no way that I know of for an unvented aluminum case to provide better cooling than a fan.
posted by trharlan at 3:35 PM on July 16, 2005

Stay far far away from Western Digital drives.

Funny, I've had the opposite experience, as have a number of server admins I know. I consider Maxtor to be the least reliable under 24/7 use for IDE drives. In general I've preferred Seagate, which goes back to SCSI days when they were the undisputed champ. But in my recent experience, WD drives have been mighty reliable. This is a personal experience, of course, and I can find no clear consensus among storage gurus. But your price-based dismissal of WD is not at all my experience. (See below.)

Fact is, all HDs fail, and more often and sooner than most people think. If this really is mission critical data, there's no way I'd keep it on a single 2.5 or 3.5 inch HD, or even on just two drives, especially if you do hot swap them and make frequent backups. The brand is less important than the redundancy.

And ejusted, could let me know where it is you find WD Caviars running less than the competition? On PCConnection, my main supplier, the 250GB WD Caviar is the most expensive single bare ATA 250GB they sell ($194), as in almost $50 more than DiamondMax and $40 more than Barracuda. I'd love to know where to get the WDs cheaper, cuz I like 'em. De gustibus . . . .
posted by realcountrymusic at 12:10 AM on July 17, 2005

PS -- of course, I don't actually pay $194 for the WD 250GB Caviars, so when I say I'd love to find them cheaper, I mean relative to Maxtor or Seagate from the same supplier. I think they end up costing me around $170 (corporate account price).
posted by realcountrymusic at 8:07 AM on July 17, 2005

realcountrymusic, dirtcheapdrives has a "special edition" for $157, which is weird, because it has more cache and a longer warranty than a more expensive version. Newegg also has good deals if you don't mind oem hd's. (No affiliation, btw, I'm just a satisfied customer). Maybe I'm just remembering that every time Fry's has a sale, WD's are always real cheap (after rebate). realcountrymusic also makes a good point about hd's failing. Backup backup backup backup and backup!
posted by edjusted at 11:24 PM on August 1, 2005