Which is quicker - A RAID Array or a Raptor?

March 18th, 2008

With desktop computers at the moment non-volatile storage options are fairly limited – and for everyday use the humble hard disk drive (HDD) is still the weapon of choice.

Hard Drives are proven performers – they’ve been around since 1956 – but they have a few limitations, mostly related to the fact that they have mechanical components:-

  1. They fail – eventually, and usually catastrophically.
  2. Their access speed is limited by the speed it takes the head to physically move across the platter and find the data you’re after – called ’seek time’

One approach to overcome these limitations is called ‘RAID’ – or a Redundant Array of Inexpensive Disks (some folks argue that Inexpensive should be Independent, but I’ll beg to differ).

In this post, I’ll be investigating ways to speed up your computer - and I’ll be test driving RAID and the fastest available single drive solution (Western Digital Raptor) along the way - let’s fish out the facts from the hype.

What is RAID?

There are several flavors of RAID, but the major ones are RAID 0, RAID 1 and RAID 10.

RAID 0 addresses the second limitation – disk access speed – basically it spreads your data across various disks (usually two but can be more) in what is known as ‘stripes‘ – basically chunks of a file. These chunks are usually quite small (64K is typical). Basically what this does is theoretically at least double the speed to access a file – you have at least two hard drives sharing the load, and as we know, two heads are better than one J

RAID 1 addresses the first limitation – failure. RAID 1 ‘mirrors’ data. Basically, when you save a file on your hard drive, RAID 1 seamlessly saves a copy on a second hard drive behind the scenes. If one drive happens to croak, the second should still have a copy, so you don’t lose your data. It’s essentially an automatic backup, and adds redundancy to your system.

RAID 10 combines the best of both worlds – it both stripes and mirrors your data – so you have a backup as well as speed boost – but you need a minimum of four disks to implement a RAID 10 array, as opposed to two for the others.

RAID has been used for ages in servers – only recently with the advent of quite quick RAID chipsets (such as the intel ICH9R) on consumer grade motherboards has it really become an option for the home user.

Alternatives to RAID for fast disk access

One other thing that you can do to speed up disk access is to increase the speed of rotation of the hard drive. The standard for a 3.5″ disk these days is around 7200 RPM – but you can get 10,000 RPM drives from western digital, and they’re known by the trade-name ‘Raptor’

The Raptor’s offer around a 25% read speed increase over 7200RPM drives for non-fragmented data on account of the fact that they rotate faster.

So which is better? RAID or Raptor?

Well – that’s a difficult question, but I can talk about the theory. In theory, A RAID 0 or RAID 10 array should be better than a Raptor because they double (or more) the bandwidth from the drives – so essentially a 2 disk RAID array should (under perfect circumstances) perform with similar speed to what a 14,400 (2*7200RPM) drive would – a raw theoretical speed increase compared to the Raptor of 50%.

Of course this relies upon a number of suppositions:-

  1. That the disks are the same size and density (the speed that the media rotates under the hard drive head decreases from the periphery of the hard drive as you reach the center – this is because of the principle of ‘tip speed’ – basically imagine you have a truck tire and a mini-moke tire next to each other. You roll each along the ground 1 revolution – which goes further? The truck tire of course – it has a larger circumference – the truck tire goes further per revolution than the mini tire – so, for a given RPM, the truck tire goes much further than the mini – it has a higher tip speed.
  2. That the actual speed of the head is equal between both disks.
  3. That there are no serious ‘bottlenecks’ in the RAID controller that limit data transfer speeds.

So let’s test this supposition.

Trial Setup

For the purposes of this trial, I took a normal desktop PC with a Gigabyte EP35C-DS3R motherboard (with intel ICH9R RAID Controller on board) with 2GB of RAM and a Q6600 Quad Core processor.

I first added a standard 7200RPM hard drive, and loaded it with windows XP – basically I didn’t want the hard drives slowed down by the OS at all, so I put it on a separate drive altogether.

I then consecutively tested each of the following as a ’secondary’ drive:-

  1. 1 x 10K RPM 150G SATA Hard Drive
  2. 4 x 7.2K RPM 500G SATAII Samsung HD501LJ hard drives in RAID 10 (64kb stripe)
  3. 2 x 7.2K RPM 500G SATAII Western Digital WD5000KS hard drives in RAID 0 (64kb stripe).

I then used a free utility called ‘HD Tune‘ to test the read speeds for each arrangement.

Results

In these results I’ll be talking about two things –

  1. Access time (the average time it takes for the head to move across the platter and find the data we’re after)
  2. Transfer Rate (the speed data is transferred in MB per second from the drive to the computer)

On the following graphs the access time is represented as a series of yellow dots, with the time on the right hand y axis.

The transfer rate is represented as a blue line, with values on the left-hand y axis.

The x axis shows the position of the head on the disk – 0% is the outside of the disk, 100% is the inside of the disk (remember, tip speed, and hence data transfer rate, decrease as we near the centre of the disk)

Test 1 – 10,000 RPM 150G Raptor.


Test 2 – 4 x 7200 RPM Samsung SpinPoint 500GB hard drives in RAID 10

Test 3 – 2 x 7200 RPM Western Digital 500GB hard drives in RAID 0

Results

In a Nutshell –

  Transfer Rate (GB/s) Access Time (ms)
Raptor 10K Max 90, Min 55 Max 17.5, min 2.5
RAID 10 (4 disks) Samsung HD501LJ Max 150, Min 75 Max 25, Min 2.5
RAID 0 (2 disks) WD WD5000KS Max 150, min 75 Max 25, Min 2.5

Access Time

The Raptor had a lower average access time across the platter than either of the RAID arrays – a good thing, BUT – there is a density difference between these drives.

If you consider that the RAID arrays are 1TB in size whereas the Raptor is 150GB in size, and look at the graphs for the RAID array you’ll see that the first 150GB of these drives (0 to 15% on the x axis) have very similar access times (probably due to the fact that the data density is higher in these drives) if not identical to the raptor.

This tells me that the heads are not as speedy on the WD and Samsung as on the raptor, but the greater data density on the high-tip speed periphery of these drives makes up for it.

Transfer Rate

The Raid Arrays comprehensively kicked the Raptors backside in sheer transfer speed – The average transfer speed was between 50 and 65% higher for a 2 disk 7200 RPM RAID Array than a Raptor Across the drive – which is in keeping with our theoretical calculations.

Additional Results –

  • There was no noticeable decrease in read performance between the RAID 10 and RAID 0 Arrays.

Recommendations – Should I use a Raptor or a RAID array?

The lower seek times for the Raptor could be useful for quick access to fragmented data – the operating system for example. On the other hand, the seek speed of the RAID arrays were just as good as the Raptor around the first 150GB of the disk, with far superior transfer rates.

If you take into account the massive cost of the Raptor (a 150GB Raptor is around the same price as two 500GB Samsung Hard Drives) it’s almost a no-brainer – go the RAID – for the same coin you’ll have 4.5 times the storage space and a much faster system – provided your files are not tiny or highly fragmented.

If you’re worried about the reduced seek speeds of the RAID array, consider partitioning your drive and using the outside sectors of the disk to host your OS.

In my case, I have two setups now – both with the same processor.

In the first, I’m using a Raptor to host my OS and a RAID 0 Array to host my documents. In the second I’ve got an unpartitioned RAID 10 array with everything - operating system and files on the one RAID volume.

I’d have to say - the RAID 10 only volume boots slightly quicker and feels generally ’snappier’ than the Raptor based system.

What I’d really like to test is a Raid of raptors J

All the best,

Matt

Digg!

Entry Filed under: Technical Tips

If you found this page useful, consider linking to it.
Simply copy and paste the code below into your web site (Ctrl+C to copy)
It will look like this: Which is quicker - A RAID Array or a Raptor?

24 Comments Add your own

  • 1. JohnMu  |  March 18th, 2008 at 8:07 pm

    I moved from a SATA RAID to a set of 3 Raptors last year. Wow, the speed is amazing. The older generation of Raptors was fairly loud, but the new ones are pretty quiet.

    Having moved almost all large files to a NAS, I don’t really need lots and lots of capacity in my system.

    I can’t wait for RAM drives to come down more in price. I tried a RAID of memory sticks, but even with fast memory sticks it’s still terrible (not to mention the limited capacity since you are mostly limited to the number of real ports… . It looked pretty cool though, lol.

  • 2. theDuck  |  March 25th, 2008 at 8:55 pm

    That’s interesting John - do you mean USB memory sticks or actual sticks of RAM? I remember reading about a company offering a battery backed up device you could plug sticks of normal DRAM into and use it to run your OS… would certainly be intereting… cripes, I’ve got about 100 PC133 sticks lying around.. I should try it when I get one of those elusive round tuits :-D

    I suspect we’ll all be laughing at the effort we went to to squeeze out a few extra % speed in a few years time - fast storage will be the next big advance I believe.

    But in the meantime - a RAID of Raptors is the closest thing to heaven I’ve heard of…

    Cheers,

    M

  • 3. TIm  |  March 27th, 2008 at 5:54 pm

    I want one of these!
    http://viroptics.blogspot.com/2007/09/fusionio-next-big-thing-in-storage.html

  • 4. NewAgeAlchemist  |  March 30th, 2008 at 6:07 am

    Just letting you know the BlitzKrieg downloads require you include BX_functions.php in the function.php for the sidebar widget to activate in WP2.5

    I’m still playing with it, so I’ll let you know if I find anything else. Great work on it though.

  • 5. Suresh M.Sc  |  April 3rd, 2008 at 4:40 am

    I think you are giving valuable info. I’m also from India. Math teacher. Helping students to do their homework.

  • 6. Jenny W  |  April 12th, 2008 at 10:14 pm

    Whoo Hoo! Found your blog! Also found your other site. not the one with the undies though…. I got a blog too, but it’s about knitting. I didn’t tell you that’s what I do when I saw you last night did I? Whoops, hope you’ll still come ’round for dinner sat and not be scared off by that little admission! Was fantastic catching up last night after all these years. Sat should be even better. Great bachelor pad by the way - can’t wait to check it out for real.

    Love peace and joy
    Jen

  • 7. Joe M.  |  April 17th, 2008 at 8:47 am

    Great article. I am a big fan of using the RAID array and currently run that in all of my server setups. I tried going with Raptor at one point and just felt like it was lacking from what I am used to. Nice write up. (EDIT:- I removed your commercial link - please respect the blog and don’t drop off topic links - doc)

  • 8. angryblue  |  April 18th, 2008 at 3:49 am

    the new version of wordpress isn’t compatible with Blix. Or at least, the new gallery feature won’t work with blix.

  • 9. Mikael Nilsson  |  April 19th, 2008 at 2:03 am

    The test seems really interesting. Couldn’t you please have the same test and meassure the startup time of Windows?

  • 10. theDuck  |  April 19th, 2008 at 2:14 am

    Your wish is my command Mikael. From pressing the button to the actual desktop (user selection off) is 23 seconds with the RAID, and 38 secs with the Raptor.

    BUT - and I repeat BUT - that’s with a brand new clean install. The RAIDS tend to get a bit segmented after time (from experiene) and you should defrag regularly.

  • 11. mike  |  May 18th, 2008 at 6:17 am

    I tried your contact form but it was broken, do you offer consulting services for seo in particular blog cosnutling I read your article on seo for WP and would like to hire you if possible?

  • 12. jalmz  |  May 20th, 2008 at 10:23 pm

    hi duck

    when are you going to update the blixtheme? compatible to 2.5 thanks

  • 13. DK  |  July 2nd, 2008 at 9:12 am

    Hello:

    Used the BlixKrieg theme with the Multiblix plugin. However, the sidebar does not appear on the non-blog pages. It looks like they should appear since the get_sidebar code is there. Any suggestions on correcting this?

    Thanks :)

  • 14. Michael Stankard  |  July 22nd, 2008 at 7:11 am

    Matt - I want to speak with you about a couple of things I need developed for WordPress. Check me out and let me know when we could have a conversation. 813-907-7688

  • 15. Craig.C  |  November 5th, 2008 at 5:54 pm

    Like a few others here, I am using this comment to contact you. When you can, shoot me off a reply.

    Thanks in advance.

  • 16. Ted  |  January 1st, 2009 at 6:30 am

    Hey Duck,

    When displaying a Flickr badge on the sidebar of your theme in IE, it does not display properly (the badge is too wide and is chopped off on the right side). Works fine in a normal post and it works fine on the side bar in Safari, Firefox and Opera.

    Any idea why the Flickr badge will not display properly on the sidebar in IE?

    Thanks much…

  • 17. CL  |  January 17th, 2009 at 1:53 am

    I have an I/O bottleneck to which I am having difficulty resolving. my short term solution is USB storage. The application is a mce machine running my movies and 1-200 recorded tv shows and comskip. My primary criteria is to keep the data and system/app on separate storage devices. the limiting factor is that the board [DEC HP Z558] only has 1 sata port, no open pci-e slots. would you recommend a raid array and if so which would fulfill my criteria? What are your thoughts on an USB raid array? I want to loose the USB storage and speed up the system by reducing the I/O bottleneck. Would you have any other suggestions?

    Please advise,

  • 18. Himanshu  |  February 26th, 2009 at 9:02 pm

    Hardware connoisseurs are very familiar with the Raptor, because it is the only 3.5″ desktop hard drive that spins at 10,000 RPM. Most desktop drives rotate at 7,200 RPM and only expensive server hard drives run faster. The first WD Raptor at 36 and 74 GB was introduced three years ago. One year ago, the Western Digital Raptor-X was introduced, offering more performance and an optional clear cover, allowing enthusiasts to look inside the drive.

  • 19. SSLVPN  |  March 29th, 2009 at 8:49 am

    Good work. I would be interested in seeing how a single Raptor performs verses dual Raptors in RAID 0 & RAID 1 configurations.

  • 20. Anon  |  March 29th, 2009 at 6:34 pm

    I recently set up RAID 0 of two 300GB VelociRaptor drives. You might be interested: http://www.abxzone.com/forums/f41/intel-dp45sg-skyburg-113330-118.html#post1433106

  • 21. Anon  |  March 29th, 2009 at 6:35 pm

    and this http://www.abxzone.com/forums/f41/intel-dp45sg-skyburg-113330-117.html#post1433089

  • 22. forexbeginer  |  May 6th, 2009 at 3:53 pm

    hmm i think Raid more better [for me]..:)

  • 23. Karthik  |  May 14th, 2009 at 7:36 pm

    Hello Guys,

    Move on, choose SSD, its heaps faster, i have two identical machines one with Raptor74GB and the other with 120GB SSD, tried booting performance with fresh install on both systems, by the time the machine with HDD displays Windows XP with status scrolling, the other has completed loading. The virus scan takes 1/3rd the time on the SSD. And the cost I dont think it is too expensive I reckon it is a bargain for the performance increase you get, I bought two raptors 74GB for about 500$ about 2 years ago, i’m not sure whats the price now, it cost me $539 to buy the SSD.

    Kart

  • 24. tips  |  January 5th, 2010 at 7:47 pm

    hi duck

    when are you going to update the blixtheme?

Leave a Comment

Required

Required, hidden

Some HTML allowed:
<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <code> <em> <i> <strike> <strong>

Trackback this post  |  Subscribe to the comments via RSS Feed


Featured Advertiser

Categories

Buy me a beer!

This sure is thirsty work - Here's your chance to buy me a beer :)

Links

Feeds

Posts by Month