RAID Scaling Charts, Part 3: 4-128 kB Stripes Compared

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Part 1 and 2 of our RAID Scaling Charts talk in detail about RAID 0, 1, 0+1, 5 and 6.

Apart from our RAID Scaling Charts, we provided a number of articles related to RAID earlier this year:

  • RAID Recovery: The Data Knight Kroll Ontrack to the Rescue
    In the event of catastrophic hard drive failure, only professional data recovery can help. During a visit to Kroll Ontrack we gained insight into how data can even be restored from a crashed RAID array.
  • Parallel Processing, Part 2: RAM and HDDs
    The second part of this article series deals with the differences between single and dual channel memory, and the performance benefits of using RAID with two or even four hard drives.
  • The RAID Migration Adventure
    All RAID arrays aren’t created equal, and as a result you may not be able to keep using your existing configuration when you update your platform.
  • Opting for RAID Level Migration
    Many SATA systems allow you to upgrade to RAID. We used hard drives with Intel and Nvidia chipsets to see how well RAID level migration could work. Our goal was simply to make storage more reliable.
  • Cheap RAID Ravages WD Raptor
    A quick hard drive such as Western Digital’s Raptor noticeably accelerates your PC, but is it still the best choice for enthusiasts?
  • RAID Boxes Run Riot
    We looked at two RAID-based external storage appliances from easyRAID and Sans Digital. They deliver increased performance, but with annoying noise levels.
  • The 2.5" vs. 3.5" RAID Challenge
  • Meet Drobo: A Data-Saving Robot
    Conventional RAID solutions can be expensive, difficult to handle and hard to upgrade. Data Robotics offers you an alternative: Drobo, a robot that will fix your storage problems.
  • Acard’s Small Business RAID Appliance
    Acard’s rackmount storage appliance uses SATA hard drives, but connects to the host system with an UltraSCSI interface. Is this the right mix for small businesses?
  • RAID on Rye
    Who said only PCs could be modded, and that server designs had to be boring? THG sits down with designer Dave Goeke, who discusses his pride and joy: a Linux file server with RAID storage in a working toaster. Or is it really a toaster in which you can store your files?

A UPS unit is extremely important to avoid data loss due to power outages.

Patrick Schmid
5 Comments Comment from the forums
  • alanmeck
    I've found conflicting opinions re stripe size, so I did my own tests (though I don't have precision measuring tools like you guys). My raid 0 is for gaming only, so all I cared about was loading time. So I used a stopwatch to measure the difference in loading times on Left 4 Dead when using 64kb and 128kb stripe size. Results, by map:
    64kb 128kb
    No Mercy No Mercy
    Level 1: 9.15 Level 1: 9.08
    Level 2: 8.31 Level 2: 8.38
    Level 3: 8.24 Level 3: 8.31
    Level 4: 8.45 Level 4: 8.45
    Level 5: 6.56 Level 5: 6.63
    Death Toll Death Toll
    Level 1: 7.75 Level 1: 7.89
    Level 2: 7.19 Level 2: 7.26
    Level 3: 9.01 Level 3: 8.94
    Level 4: 9.36 Level 4: 9.36
    Level 5: 9.5 Level 5: 9.64
    Dead Air Dead Air
    Level 1: 7.68 Level 1: 7.47
    Level 2: 7.96 Level 2: 8.03
    Level 3: 9.08 Level 3: 8.87
    Level 4: 8.17 Level 4: 8.17
    Level 5: 6.98 Level 5: 6.84
    Blood Harvest Blood Harvest
    Level 1: 8.24 Level 1: 8.17
    Level 2: 7.33 Level 2: 7.33
    Level 3: 7.68 Level 3: 7.68
    Level 4: 8.45 Level 4: 8.31
    Level 5: 7.89 Level 5: 8.1

    I'm using software raid 0 on my GA-870A-UD3 mobo. The results for me were almost identical (128kb was faster by .07 seconds total). That being the case, I erred on the side of 128kb in order to reduce the potential for write amplification (I'm using 3x ocz vertex 2's). What's remarkable is that, despite using the stopwatch to measure times manually, the results were always either identical, or separated by intervals of .07 seconds. Weird, huh? Btw thanks to Tomshardware, you guys give a lot of helpful info.
    Reply
  • Does anyone want a slower system? why do we have to choose? why do we not just get the fastest option without having to do this? or is that to simple!
    Reply
  • I wish we could see what 256 does. Or even 1024 but that just sounds like a waste of space unless your doing Video or Music. Maybe gameing but RAM and bandwidth will always give you an edge if no one is hacked the game.
    Reply
  • Shomare
    I agree...can you please look into getting one of the new Areca 1882 controllers with 1+GB of mem on it and a dual core 800Ghz processor? We would like to see the larger stripe sizes, the larger processor, and the larger memory footprint's results! :)
    Reply
  • dermoth
    There is a misconception in this article. The point about capacity used: "For example, if you selected a 64 kB stripe size and you store a 2 kB text file, this file will occupy 64 kB.". This is totally wrong.

    The only incidence on size used is the FILESYSTEM block size as all files stored will be rounded up to the upper block (the last block being only partially filled). To the OS, the RAID array still looks like any other storage device and multiple filesystems block can be stored within a single stripe element.

    Also note that on RAID 5 & 6, the stripe size is the stripe element size X number of data disks, and writes are fastest when full stripes are written at once. If you write only 4k in a 384k stripe (ex 64k stripe element on a 8-disk RAID6) then all other sectors have to be read on disk before the controller can write out the 4k block & updated parity data.

    You will get better performance if you manage to match the filesystem block size to the FULL raid stripe size, and only in that case the statement above is true. Many filesystems offers other means of tuning the filesystem IO access patterns to match the underlying RAID geography without having to use excessively large block sizes, and most filesystems default to 4k block sizes which is also what most standalone rotational medias use internally since many years (even when they show 512k sector sizes for compatibility).
    Reply