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Pleonasm

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RAID 0: Any Benefit for a PC User?
Apr 10^th, 2007 at 3:05pm

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The enthusiasm of the power user community combined with the marketing apparatus of firms catering to such crowds has led to an extraordinarily erroneous belief that striping data across two or more drives yields significant performance benefits for the majority of non-server uses. This could not be farther from the truth! Non-server use, even in heavy multitasking situations, generates lower-depth, highly-localized access patterns where read-ahead and write-back strategies dominate. Theory has told those willing to listen that striping does not yield significant performance benefits. Some time ago, a controlled, empirical test backed what theory suggested. Doubts still lingered - irrationally, many believed that results would somehow be different if the array was based off of an SATA or SCSI interface. As shown above, the results are the same. Save your time, money and data - leave RAID for the servers!

Source: http://www.storagereview.com/articles/200406/20040625TCQ_6.html

It is true? Does RAID 0 fail to deliver a meaningful performance gain in a single-user PC environment?

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MrMagoo

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Re: RAID 0: Any Benefit for a PC User?
Reply #1 - Apr 10^th, 2007 at 9:04pm

I can't say that I've ever done performance tests, but I run RAID 0 on my desktop and feel it gives me significant performance gains. When I initially set it up, I was still running Windows on my desktop. A clean install took much less time (about 9 minutes as opposed to 21 minutes, if memory serves me right.) Windows also felt zippier, not unlike how Rad describes using a SCSI drive. I've never run Linux on my desktop without RAID, so I really can't say if its making a difference, but I do get good performance despite my middle of the road hardware.

I'd like to know what the "controlled, empirical test" was that he mentions. Its possible the the RAID array in the test didn't deliver significant performance increases because the information bottleneck in the system used in the test was not the hard drive. I've seen situations were the front side bus wasn't fast enough to keep up with the demands of the rest of the computer, in which case a faster hard drive wouldn't change anything.

It also makes a big difference if you are using an add-on controller card or if it is built onto the motherborad. When I used an add-on card, I got a noticeable performance boost over non-raid. I got another noticeable boost when I installed a new board with integrated SATA (same hard drives, but the processor was faster, so its hard to compare without drive performance testing, which I never did.) My thought at the time was that the information bottleneck was probably on the PCI bus with the add-on card.

If you know of any good drive performance tests, I could run a few and then we could compare them to what you would expect of similar hardware without RAID. The only stipulation is that the tests need to be Linux compatible (ext3 filesystem.)

Come to think of it, I have an open 500 MB partition that is not RAIDed. I could install a second instance of my OS on it and re-run the tests. Might be an interesting weekend project...

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nbree

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Re: RAID 0: Any Benefit for a PC User?
Reply #2 - Apr 10^th, 2007 at 9:34pm

Quote:

It is true? Does RAID 0 fail to deliver a meaningful performance gain in a single-user PC environment?

The money part of the quote is "the majority of non-server uses". Unfortunately, since the links in the article are busted, we can't see what he means by that. It's also a little problematic because the article is so damn old, and the Highpoint's tested are really low-end gear.

Where you can see real, major, unarguable benefits from striping is gaming - precisely the application the high-end PC enthusiast cares about most, in my experience. The volume of texture and level data that modern games are streaming off disk nowadays is pretty impressive. Even an older game like Everquest is hitting about half a gig of data every time you zone, all in nice big stripe-friendly chunks.

The same developer at work who I mentioned had the 3Ware controller uses an 0+1 array and plays World of Warcraft. Whether that fits "the majority of non-server uses" is arguable, but gaming is a major driver of demand for high-end PC componentry and there some notable games that do benefit.

Similarly, another community that I know of where striping has long been standard practice was video enthusiasts. 10 years ago when I started working with miniDV striping was damn near something you HAD to do in order to deal with DV streams; these days normal transfer rates make miniDV an non-issue but instead we're talking about wanting to manipulate big chunks of HiDef instead.

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Rad

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Re: RAID 0: Any Benefit for a PC User?
Reply #3 - Apr 11^th, 2007 at 12:02am

Quote:

[quote]Even an older game like Everquest is hitting about half a gig of data every time you zone, all in nice big stripe-friendly chunks.

like nbree says, it depends on what kind of files you're shuttling with the stripe. big files make better use of a stripe. video works great on stripes. so does audio. even large graphics files, as nbree described.

back in the day, storage review was run by two guys. when sr hit hard times, one of them left. eugene stayed. he has always poo-poo'ed both scsi & raid.the other guy liked scsi.

i've never used raid, but looked into it, thinking of settting up a stripe ..just to say i did .. the fault intolerance was the thing i couldn't get over. but i know the theory.

Edited:

oh, i see nbree mentioned video, too.

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Pleonasm

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	Re: RAID 0: Any Benefit for a PC User? Reply #4 - Apr 12^th, 2007 at 12:24pm Readers of this thread may be interested in the article RAID Or Raptor? that explores the advantages/disadvantages of using one WD Raptor versus a RAID 0 configuration of two SATA drives.
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MrMagoo

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	Re: RAID 0: Any Benefit for a PC User? Reply #5 - Apr 12^th, 2007 at 8:11pm I would be interested in the performance or RAIDed Raptors...
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Re: RAID 0: Any Benefit for a PC User?
Reply #6 - Apr 12^th, 2007 at 8:27pm

the article is from feb '06.

from the last page (14/14, conclusion):

Quote:

Finally, we have a new high-performance enthusiast hard drive that is capable of beating its competition in the blink of an eye. Of course it's the high rotation speed of 10,000 RPM that lets the Raptor perform noticeably better than any 7,200 RPM drive in everyday uses. This applies to both access time and data transfer performance, and it helps to further reduce the annoying little delays inherent in everyday PC operation.

note: "Of course it's the

high rotation speed

... that lets the Raptor perform noticeably better than..."

and

"This applies to both

access time and data transfer

performance, and it helps to further

reduce the annoying little delays

" (i.e > responsiveness .. the thing i've been talking about with scsi)

anybody think of 15k-rpm SCSI when they read that?

(i did)

http://www.tomshardware.com/2006/02/06/wd1500ad_raptor_xtends_performance_lead/p...

if the rpm (10K) is what makes it better than a 7200-rpm drive, then the same would apply to a 15k-rpm drive.

again, i need to say that i'm most interested in *reliability* now.

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Pleonasm

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Re: RAID 0: Any Benefit for a PC User?
Reply #7 - Apr 12^th, 2007 at 9:32pm

Rad, it is (obviously) the case that 15K RPM is better than a 10K RPM specification for a hard disk drive. But, as we discussed in this thread, the SAS/SCSI drives are optimized for the server environment whereas the SATA drives are optimized for the single-user environment. (There are, I understand, a few exceptions of SAS/SCSI drives that can be switched from one mode to the other.) As a consequence, this is a case – in my opinion – in which a higher technical specification doesn't translate into better real-world improved performance. It is not dissimilar to running a single-threaded application on a dual-core versus single-core processor: although the former is technically superior, it is not going to deliver any real-world performance enhancement as compared to the latter.

Although it is not an independent assessment, note that Western Digital makes this claim:

Quote:

WD produces the world’s most reliable SATA drives. With 1.2 million hours MTBF, enterprise duty cycle, 5-year limited warranty, next-generation SATA technology, and state-of-the-art vibration tolerance, WD Raptor drives offer the best combination of reliability, high capacity, and performance for enterprise applications. …

Key Features: Reliable – Designed and manufactured to enterprise-class standards to provide enterprise reliability in high duty cycle environments.

Source: WD Raptor

By the way, I do not now use the Raptor drive myself – but, will most likely configure my next PC purchase to include it.

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Pleonasm

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Re: RAID 0: Any Benefit for a PC User?
Reply #8 - Apr 12^th, 2007 at 9:48pm

Interestingly, the article WD Raptor RAID Performance shows that two WD Raptor SATA drives in RAID 0 perform better than two Seagate Cheetah SCSI drives in the same configuration – and, with both running at 10K RPM. Thus, when the RPM factor is held constant, SATA still outperforms SCSI in the single-user environment.

Readers of this thread may also be interested in: "Who Says 2 Raptors Aren't Better Than One?"

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Rad

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Re: RAID 0: Any Benefit for a PC User?
Reply #9 - Apr 12^th, 2007 at 9:54pm

Quote:

Designed and manufactured to enterprise-class standards to provide enterprise reliability in high duty cycle environments.

interesting statement. they are coming right out and saying "we build these things like scsi drives."

i should not however, that wd is one of the few hd manufacturers that *doesn't* make scsi drives. and just cuz the make a claim doesn't mean it's true.

but they got my attention by merely making the claim.

here's what i think. if you built two identical systems (a and b) with the sole exception that one had a 15k-rpm scsi beast, and another had a raptor (latest generation) .. to run the o/s, prgms & page file .. and you sat down a series of power users at each and let them do a bunch of stuff that they normally do .. i'd wager most (if not all) came away saying the scsi-based systems "felt faster".

of course, i'm talking about applications that require a lot of disk activity (the more the better) .. not just checking email & surfing the web.

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Pleonasm

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Re: RAID 0: Any Benefit for a PC User?
Reply #10 - Apr 13^th, 2007 at 9:28am

Rad, while Western Digital’s claim is clearly self-serving, one would expect that the company’s attorneys have vetted the statement based upon evidence – otherwise, the firm would be inviting legal action against itself.

It is also worthwhile to recall that Western Digital didn’t originally create the Raptor for PC enthusiasts – rather, it was designed for the commercial (not consumer) audience. It was literally an unanticipated surprise to the company that the Raptor became such a success in the PC arena.

Some have said that the only reason why other manufacturers do not make Raptor-class SATA drives is that by so doing they would negatively impact the sale of their own SCSI drives (i.e., they would be creating their own competition). Western Digital, in contrast, does not have this “conflict of interest” because it does not manufacture SCSI units.

Your “wager” in Reply #9 is interesting. All of the benchmark data that I have seen strongly suggest that that the Raptor would be perceived as the “winner” in such a comparison involving a single-user PC. I do not understand: why might anyone expect otherwise?

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Re: RAID 0: Any Benefit for a PC User?
Reply #11 - Apr 13^th, 2007 at 12:21pm

Some balanced commentary on the subject . . .

Quote:

If we're looking at just the hard disks alone, the Seagate Cheetah X15.3 is clearly the more impressive of the two models. Despite increasing competition from Western Digital, the Cheetah X15.3 retains it's dominance of the high-performance personal storage market. With faster spindle speeds and lower access / seek times, the Cheetah can indeed push some very impressive benchmark numbers. Nevertheless, in day to day usage, we did not find the Cheetah to be that much faster compared to the Raptor.

The Raptor is an impressive disk in its own right. Faster and quieter than its predecessor, the Raptor mixes mature 10K RPM technology with a new Serial ATA/150 interface. The Raptor 74GB is about the same price as a 74GB 10K RPM SCSI disk, but without the added cost of a SCSI controller, the Raptor is much more attractive to gamers and workstation users. The Raptor’s transfer rates on average are about 15% slower compared to the Cheetah X15.3, but the Raptor still dominates over the landscape of 7,200 RPM drives on the market. For everyday tasks, the Raptor “feels” like a high-end SCSI disk, and performs like one as well.

It’s hard to recommend the Cheetah X15.3 right now – since the Western Digital Raptor really does come close to the Cheetah in terms of disk performance, and costs so much less. The Raptor runs quieter and cooler, and is much less expensive. The Cheetah X15.3 will still hold a niche market for those who need insanely fast data access, but the Raptor has proven itself to be fast enough for servers and workstation users alike.

Source: Raptor WD740 vs. Cheetah X15.3

P.S.: Note the date of the above article (3/30/2004) and the fact that it is using the WD740GD model, a second-generation unit. If the same test was repeated with the third-generation WD740ADFD model, the differences with the SAS drive would have been further minimized.

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Pleonasm

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Re: RAID 0: Any Benefit for a PC User?
Reply #12 - Apr 14^th, 2007 at 5:21pm

Rad, here is an article that supports the superiority of the SAS Seagate Cheetah 15K over the SATA Western Digital Raptor:

Quote:

As we saw by our benchmarks, SCSI is still on tops when it comes to raw performance, as the Cheetah 15K series drives can outperform SATA’s fastest Raptor disks by quite a large margin. In most of our tests, even two Raptor drives in RAID-0 will perform about the same (or a bit below) a single Cheetah 15K drive in a non-RAID configuration.

Source: Bleeding Edge Storage

Note also that Seagate describes the Cheetah 15K as having the "Highest reliability rating in the industry."

Confusing, isn't it?

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	Re: RAID 0: Any Benefit for a PC User? Reply #13 - Apr 15^th, 2007 at 12:13am Great link. That article does a great job of showing the difference between SATA and SAS and the advantages of each. It almost makes we want to build a new computer...
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Re: RAID 0: Any Benefit for a PC User?
Reply #14 - Apr 17^th, 2007 at 2:14pm

Several years ago, I listened to the Hype about Raid being so fast.
Fortunately, I made a Ghost Image of my HD before I set up the Raid (stripped) configuration.
Using two drives to do the work of one seemed sort of nonsensical to me at the time.
I never saw the blinding speed I'd been told that I'd have with a raid setup. So after several weeks, I put the system back in a two drive, master and slave config. That was with two IDE drives.

Months later when I began using SATA drives, I once again tried the RAID thing. Once again, all the hassle of setting it up just wasn't worth it. I never did see the speed promised.
Once again after several days, I returned my system to a single drive for my OS.
A single OS drive is so much easier to maintain.
The greatest speed increase in a hard drive that this tech has ever seen is when I went to a Maxtor SATA II/300 hard drive. I now run two of them, one each in my two main PC's. I back them up using two Maxtor IDE/133 drives, run through IDE to SATA dongles, to increase data transfer speeds to 1500mbps.
That's right.....SATA speed out of an IDE/133 drive. It blew my mind when I first saw it.

So my conclusion is that there will be no more RAID here. Only, SATA II/300 drives from now on, till something even faster comes along. At less than $100 each, my two Maxtor 200gig SATA II/300 (3000mbps) drives, are the best investment in HD storage that I've ever made.

Thank you all for this great forum.

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