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ErgloadErgload Member UncommonPosts: 433
I read somewhere (I don't know if it's here) that two WD Blacks on RAID would pretty much be as good as an SSD while offering twice or three times more storage at a much lower price. Anyone here have any experience with RAID setups that could help me out?


  • QuizzicalQuizzical Member LegendaryPosts: 20,974
    What you read is completely wrong, outside of certain use cases where your drive accesses are almost purely sequential.  Hard drives are fine for things like recording video, but you don't want to run real programs off of them, and RAID does nothing to help with that.

    The problem with hard drives is that, if you want to grab something, you have to wait for a platter to physically spin to the right spot and the drive head to move to the right spot before it can even start reading.  That takes on the order of 10 ms.  On an SSD, you don't have to wait for hardware to physically move around, so your small read can be done entirely in about 0.1 ms.  Now, 10 ms may sound fast, but what happens when you have to load 1000 things at a time, for example, when loading or zoning in a game?  1000 * 10 ms is now 10 seconds, and so you get to sit and wait.  On the SSD, you're looking at well under 1 second--likely fast enough that storage isn't the bottleneck at all.

    RAID can help with sequential reads and writes, but not random.  If some reads go to one disk and others go to the other, you still have to wait that 10 ms for one hard drive to physically spin to the right spot.  Depending on how big the read is and how they're striped, you might have to wait for both drives to physically spin to the right spot.

    Meanwhile, if you get RAID 0, then either drive failing means all of your data is gone.  Even if both drives are individually fine, sometimes the RAID array gets messed up and it still doesn't work.  You don't want to fuss with that if you don't have to.  RAID 5 or RAID 6 avoid those problems, but if the checking is done in software, that's a lot of overhead which slows everything down.  A dedicated RAID controller can avoid that drawback, but last time I checked, those cost around $300 and up.  That's fine for a $20000 server, but not what you want for consumer use.
  • ErgloadErgload Member UncommonPosts: 433
    I see. That explains it. Now I can call BS if I ever see the guy who said that two Blacks on RAID was as good as an SSD.
  • RidelynnRidelynn Member EpicPosts: 6,825
    They probably will meet or beat an SSD in sequential read/write, but that is just a benchmark number - real world performance is more dependent on random seek time, since your system usually hammers for hundreds (or more) files at a time when it does things like boot up, start programs, etc.
  • CleffyCleffy Member RarePosts: 6,047
    You actually need 4 for sequential read/write to match an SSD. Each desktop HDD also consumes 4 times more energy. So you are looking at a Raid array consuming 16 times as much energy around 40 watts to do what a single SSD is doing better at 2.5 watts.
    The main advantages of an HDD are price per GB and reliability. You strip away the reliability when you raid. They are optimal for storing data. With how cloud storage is today, I have completely dropped my HDDs. Keep my unsecure stuff on cloud, and secure stuff on my SSD. The price per GB equation is also a lot cheaper considering you can get 750 GB for around $200 today.
  • HrimnirHrimnir Member RarePosts: 2,413

    Yeah, as everyone else said, not even REMOTELY close in performance, whether it's sustained transfer speeds (read or write) or random access/IOPS.  Particularly the latter, SSD's blow HDD's out of the water in random reads/writes, etc.

    SSD's are at a point where unless you are being lazy and or reckless with your game installs (i.e. having 50 games installed at once and stuff you haven't played in months/years) you can't possibly justify the need for more than around 500gb SSD or MAYBE a 1tb.  a 500gb SSD can be had around $150 bucks, yes, that will buy you a 2tb+ WD black, but performance isn't even in the same galaxy.

    "The surest way to corrupt a youth is to instruct him to hold in higher esteem those who think alike than those who think differently."

    - Friedrich Nietzsche

  • DeivosDeivos Member EpicPosts: 3,692
    Hrimnir said:

    ...unless you are being lazy and or reckless with your game installs (i.e. having 50 games installed at once and stuff you haven't played in months/years) ....

    *hides the 4tb of game data I have on my PC*

    "The knowledge of the theory of logic has no tendency whatever to make men good reasoners." - Thomas B. Macaulay

    "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge." - Daniel J. Boorstin

  • DMKanoDMKano Member LegendaryPosts: 21,169
    edited June 2016
    The time of platter based hard drives is coming to an end.
    Not buying an SSD at this point would just be ill advised.

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