Western Digital's Raptors in RAID-0: Are two drives better than one?
by Anand Lal Shimpi on July 1, 2004 12:00 PM EST- Posted in
- Storage
Parallelism has been a topic of interest within the PC technology industry ever since its inception. The basic principle of computing is to accomplish incredibly large and complicated tasks through the completion of smaller individual tasks, which in some cases, can be executed concurrently to maximize performance. We've seen examples of exploiting parallelism in computing with technologies such as multiprocessor systems, Hyper Threading and, of course, the long-missed Voodoo2 SLI.
The benefits of parallelism vary depending on the application. For example, the impact of dual processors or a Hyper Threading enabled CPU can be as little as 5% for a normal desktop user, but as much as 50% for a server system. Graphics rendering is virtually infinitely parallelizable, with a doubling in raw GPU power resulting in close to a doubling of performance. But what about hard drive performance? Are two drives better than one?
Of course, the technology that we are talking about is RAID, standing for Redundant Array of Independent (or Inexpensive) Disks. As the name implies, the technology was introduced for redundancy, but has morphed into a cheap way to add performance to your system. With the introduction of their 875P/865 chipsets, Intel brought the two simplest forms of RAID to desktop users for free: RAID 0 and RAID 1. With the majority of Intel's chipset shipments featuring RAID support, desktop users are beginning to experiment, now more than ever, with RAID as a method of increasing performance.
On paper, RAID can provide dramatic increases in performance. But as we've shown in our other hard drive reviews, the real world often differs greatly from the realm of synthetic disk benchmarks. So, what happens when you measure the real-world impact of RAID on today's fastest, most disk limited systems? Should we all start buying two hard drives instead of one? Or should RAID still be used for redundancy and not for performance when it comes to the average desktop user?
Let's find out...
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Kaido - Thursday, July 1, 2004 - link
Wow, this article's conclusions were nice to know...I had wanted to do this.My other idea was to get three of them in RAID 5...how would that compare to a single drive? (It'll take a bit more saving tho lol)
Also, what's the best RAID controller, or does it matter?
ranger203 - Thursday, July 1, 2004 - link
How come they didn't post the raid setup.... i mean anyone that uses it knows there there is a difference between 64K stripe and like 512K....Pumpkinierre - Thursday, July 1, 2004 - link
Yeah I agree something's wrong with this article. Anand needs to check his setup closely.Insomniac, #14 you were right first time: if you had a slower disc in an intelligent RAID1, you ought to read from the faster disc exclusively (I dont say that present controllers can). Also your suggestion on striped reads in RAID1 is good and mentioned also by Arth 1 #34. But as far as I am aware inexplicably RAID1 doesnt do this anymore (perhaps on more expensive controllers) see:
http://arstechnica.com/paedia/r/raid-2.html
"I should note that this discussion is based on the more recent, er, modern definition of RAID 1. The original model for this config actually included striping (as in RAID 0), and not simply "disk duplexing." In the end, however, the duplexing model is what the industry uses, and RAID 1 is synonymous with that. Therefore, notice that RAID 1's contribution to the world of storage technology is the principle of data mirroring"
But they do say earlier and strangely:
"Now here's an oddity: a read transaction can theoretically occur twice as fast as on single disk. Hence RAID 1 is often used on low-end web servers. The read performance is standard, if not better than single disk performance, and the poorer write performance is largely irrelevant on most web servers (save those doing transactions, of course). RAID 1 configs are great for mid-volume FTP servers as well."
From what I gather modern implementations of Raid1 are only a little better at reads due to the extra buffering and faster controllers. In terms of RAID, a RAID1 with virtually striped disks is the way to go for a gamer. It ought to give you faster loads as well as backup at the cost of slightly slower writes (not a great problem for gamers) and smaller storage (doesnt matter- cheap big HDDs nowadays). Yet it all but seems to be ignored by the manufacturers and IT industry as only relevant to servers.
madgonad - Thursday, July 1, 2004 - link
As much as I usually agree with articles posted here, I think the reviewer wasn't thinking clearly.My point is that RAID-0 is most obviously beneficial when working with LARGE files; big Photoshop tiffs, RAW audio files, video, and 3D graphics. Running tests that make use of office applications aren't going to demonstrate the arrays function. Kind of like driving a Ferrari in a residential neighborhood isn't going to demonstrate any real performance.
My computer has three identical 160GB drives. Two are in a RAID-0 array and the third is my 'mirror' where art and other important files are backed up. Pulling the exact same file from the working array takes about half the time as it takes when pulling it off of the backup drive without the array. Exactly what would be expected. If you need more speed in loading/saving large files then RAID-0 is for you. Since none of the tests in the article test this obvious advantage I would have to say that the test is either flawed or the writer didn't think through what a RAID-0 array is best at.
binger - Thursday, July 1, 2004 - link
those that whine about anand not using a hardware raid controller in this test, check out the storagereview article @ http://www.storagereview.com/articles/200406/20040...they use a promise hardware controller and reach the same conclusion.
thatsright - Thursday, July 1, 2004 - link
I waited a long time to see a article like this on AT, because I can expect a fair handed and comprehensive review, Not this TIME!!This article has got to be the most Shoddy, rushed piece I have ever read on AT. It really seems like a Tom's Hardware article.
qooleot - Thursday, July 1, 2004 - link
In this article today you guys write:If you haven't gotten the hint by now, we'll spell it out for you: there is no place, and no need for a RAID-0 array on a desktop computer. The real world performance increases are negligible at best and the reduction in reliability, thanks to a halving of the mean time between failure, makes RAID-0 far from worth it on the desktop.
And in another article:
Recommended: Dual Western Digital Raptor 74GB 10,000RPM SATA in RAID 0 Configuration
Pariah - Thursday, July 1, 2004 - link
"I really wish some regular 7200 RPM drives had been used, considering someone who can afford a 74GB Raptor won't care about the costs of RAID anyway."Wouldn't make any difference, you can extrapolate the performance of 7200RPM drives by looking at the improvement of the Raptor from one drive to 2 drives. You're not going to see a 5% increase with the Raptor and a 45% increase with 7200 or -30% loss. You'll see just about the same increase/decrease.
"I thought if it was smart, it would use both drives and improve performance."
True, IF it was smart. Unfortunately, basically every ATA/SATA RAID controller does NOT load balance reads in RAID 1. 3Ware controllers do and Highpoint controllers that advertise RAID "1.5" support do as well, I'm not aware of any others that do, though there may be random other models.
"If that wasn't the case, I wondered if you could choose which drive it read from."
No, there is no "drive affinity" setting for RAID arrays.
"But the one really fundamental thing wrong with the whole comparison is that you didn't actually compare RAID0 with a decent RAID 0 card like HighPoint RocketRAID."
Changing the controller would make pretty much no difference whatsoever for the configuration that was tested in the article (2 drive RAID 0 array). Software cards will perform just as well as a $500 3Ware card in 2 drive RAID 0 arrays. As you add drives and use increasingly complex RAID levels, then the controller will play a significant role in overall performance.
"Why bother to waste space describing in detail the differences between RAID 1 & 0 if no benchmarks from a RAID 1 are going to be included in the article??"
I agree, didn't understand that myself.
"AND the differences in CPU utilization between them. Most of the onboard soloutions are actually SOFTWARE RAID's as compared to a true dedicated hardware device."
For RAID 0 and even more so for RAID 1, CPU utilization is irrelevant as far as the controller is concerned, because there are practically no calculations necessary for a 2 drive RAID 0 array. For RAID 1, there really aren't any at all.
"I use 2 Seagate 15k.3's in RAID0 on a Adaptec 39320 Host RAID device. It sure feels faster than a single drive to me."
Can you say placebo? Sorry to hear you wasted your money on a garbage controller like that. Adaptec controllers are widely know to be horrendous performers. Adaptec is the only company I'm aware of that has released RAID controllers for any interface that actually don't perform better in even lowlevel benchmarks in RAID 0 than they would with just a single drive.
"Onboard RAID (and most cheap raid cards such as Promise) are technically software RAID cards and usually do not offer any speed increases over 5%. True hardware RAID cards offer speed increases at about 40% (as shown in the past)."
Maybe 5+ years ago, with a Pentium 90 and non-DMA ATA drives. Not true at all anymore. Moving to hardware for a simple RAID 0 array will net you nothing in additional performance.
"I was suprised not to see any Iometer benchmarks. IOPS and response times are king in determining disk performance. Iometer is still the best tool, as you can configure workers match typical workloads."
IOMeter is a glorified access time benchmark that doesn't give anything in the way of useful applicable results for home users.
Though the results of the article are not surprising, it was still a pretty poor read overall. Anandtech needs some more work on its storage articles if it wants to catch up to other sites like SR, Tech-Report and Digit-Life. The overall knowledge displayed in articles is noticeably lacking, well below the standards set in its CPU and video card articles.
ir0nw0lf - Thursday, July 1, 2004 - link
Why does this site blast a Raptor RAID-0 array in this article so badly and recommend a Raptor RAID-0 array in their high-end buyer's guide so highly? Seems like a massive 180-degree shift to me. Very curious...rjm55 - Thursday, July 1, 2004 - link
The major problem I have with this article is that 20% to 38% improvement in IO operations with RAID 0 in the first benchmarks is ignored as "not much", and then the "Proof" that RAID O doesn't improve performance is Winstones and SysMark which are sequential or linear benchmarks. I can also tell you that Winstones and Sysmark provide about the same scores with on-board Intel video as they do with an X800 XT and this does NOT prove to me that high-end graphics are a waste of money, it just proves that Winstones and Sysmark are not a good tool to measure graphics perfomance.The review seems far too strained to prove a pre-concluded idea, IMHO, and really doesn't prove anything except Winstones and Sysmark are terrible tools for comparing Hard Drive performance. The tests in Winstones, as i understand them, are not my real world, they are office-worker-running-one task-at-a-time world. I DO multitask on my computer, as do most users today, and this is where RAID 0 DOES make a difference. Where are benchmarks that compare performance in multitasking situations?