Putting the Redundancy in RAID: RAID-1

The next type of RAID that we'll talk about is RAID-1, otherwise known as mirroring. We won't be benchmarking RAID-1 here because, for the most part, there's no performance increase or decrease. As the title of this page implies, RAID-1 is done for redundancy.

Writing to a two-drive RAID-1 array

Unlike RAID-0, there is no preprocessing done on the data before it is sent to the hard drives. Instead, with RAID-1, a duplicate of everything written to drive 0 is written to its mirror drive. The benefit of RAID-1 is that if one drive fails, you have a perfectly working backup that can take over until you have replaced the failed drive. You have effectively doubled a single hard drive's mean time between failure by using two in a RAID-1 array. You'll notice that this is the exact opposite of RAID-0, but the downside to RAID-1 is that you spend twice as much on hard drives without getting any additional capacity or performance, just reliability.

Doubling Theoretical Performance: RAID-0 The Test
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  • Runamile - Thursday, July 1, 2004 - link

    I liked the diagrams for RAID0 and 1. Would be cool to see 3,4,5, and 10 drawn out too, but that wouldn't of been relevent to the article.
  • ciwell - Thursday, July 1, 2004 - link

    Excellent article...and for those who think it is faster experientially: it is all in your head. ;)
  • SilverBack - Thursday, July 1, 2004 - link

    I'm using two RAID 0 arrays.
    A8V mobo with a promise 378 controller and the onboard VIA as well.

    I prefer the system this way. It just makes the whole windows experience faster.

  • RebolMan - Thursday, July 1, 2004 - link

    Any subjective comments on whether the system using RAID-0 feels any smoother? A lot of people comment that P4s with Hyperthreading produce a system that just feels more responsive regardless of whether it's really any faster.

    I find the best thing to do (under Windows) when you've got two drives hooked up is to move your Virtual memory onto the one which you use less. There's all sorts of tricks you can use to distribute your system load without necessarilly using RAID.
  • wanosd - Wednesday, August 4, 2010 - link

    I recently did a test by copying a few GB of data from a WD 160 GB drive to another WD 160 GB drive. It took about 4 mins.

    I then renamed the folder that I just copied and then copied it back to the original drive, and again got about the same time, with only a few seconds difference.

    I timed my boot from Windows from the time the OS takes over, all the way to the desktop, and it took about 35 seconds. I do NOT have any bloatware or junk on my system.

    Finally, I enabled RAID 0 for these two drives. Now the same version of Windows boots up in about 25 seconds (not as fast as you'd think). Also, copying the same folder from my 3rd hard drive to my RAID 0 drives is taking 1 minute and 45 seconds. The seek time itself may be still slow, but once you get the data going, it'll definitely help out.
  • qepsilonp - Monday, October 31, 2011 - link

    I play eve online and i can be running at any given time 3 clients of eve a music player / video / or a text to speech program a browsing client with usually 5 - 7 tabs and sometimes i even want to be able to extract files at the same time I think for that kind of usage RAID 0 would be very worth it, did you even consider a lot of users do multiple demanding tasks at once?
  • qepsilonp - Saturday, November 5, 2011 - link

    while yes when running one application RAID 0 is usually useless but when like me most of the time you are using 2-3 clients of a heavily HDD relent game where sometimes it takes a while to get the files for the 3D images and sometimes because of that your they wont show up on the screen for sometimes 5 seconds and i know its not anything else but the HDD because i have a new computer and the only piece of hardware that hasn't been updated is the HDD and im still getting it.

    if i was able i would also be running a HD movie or have my computer read a book to me with a text to speech program or be playing music and also maybe extracting something with Winrar you cant tell me that with all those IO's that RAID 0 wouldn't help at all, considering the game im playing is eve online and when i jump in and a gate can have 1000 ships on it thats maybe 32 different ships types which have to be gotten from the HD which is probably something like 100mb times 2 - 3 thats 64 to 96 IO's thats if theres isnt multiple files that need to be called up for 1 ship type so yeah I think in the deck top for power users there is a place for RAID 0

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