To RAID or not to RAID

This is a discussion on To RAID or not to RAID within the A Brief History of Cprogramming.com forums, part of the Community Boards category; Hi, I am on the cusp of possibly doing a RAID 0 between two 500 gb hard drives. The primary ...

  1. #1
    Linguistic Engineer... doubleanti's Avatar
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    To RAID or not to RAID

    Hi,

    I am on the cusp of possibly doing a RAID 0 between two 500 gb hard drives. The primary reason I want to do this is two fold. First, it'd be nice to have faster boot time. Second, and the main concern, is that I'd be able to read and write things (hopefully) twice as fast for research purposes.

    So I had just convinced myself to do this, when I thought to myself "what if I just run two processes on seperate drives". Would that do the trick, without having to RAID?

    Does any one have any experience with RAID?

    Thanks!
    hasafraggin shizigishin oppashigger...

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    How exactly do you "run two processes on separate drives"?

    If, by research, you mean you are writing programs that access disks a lot, making them access different drives will definitely help.

    On my server I have tried RAID-0 for system drive, and RAID-1 for data. RAID-0 gives you about 160% the performance of single drive, so it definitely helps. RAID-1 gives slightly lower write performance (than single drive), but also ~160% read performance.

    I am currently running RAID-5 with 3 drives. Same as RAID-1 (fast read, slow writes).

    If you already have a RAID controller (or have one built-in to your motherboard, or is running Linux), why not give it a try?

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    Here are the results of my testing using 3 HD's in RAID 0, 1, & 5 as well as non-RAID:
    Seagate Disk & RAID solutions - Comparison of RAID 0, 1 & 5
    "I am probably the laziest programmer on the planet, a fact with which anyone who has ever seen my code will agree." - esbo, 11/15/2008

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    Linguistic Engineer... doubleanti's Avatar
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    Hm... ok well, I have a 750 gb, and two 500 gb drives. So that means I'll be wasting 250 gb on the largest drive since raid 0 truncates it to 500, like the others.

    Is there a way around this? I don't mind it much. Also when doing this, during one of the reboots in Vista it hangs at "verifying DMI pool data". Any ideas?

    Thirdly, is there a way to do a raid 0 on the two 500 gb drives, and no raid at all on the 750 drive? This would be ideal for me.
    hasafraggin shizigishin oppashigger...

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    AFAIK that is a limitation of all hardware implementations (size of smallest disk).

    Linux software RAID doesn't have this limitation.

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    Wait... I know that avatar! Where on earth have you been!? </off-topic>

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    Linguistic Engineer... doubleanti's Avatar
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    Well, I figured it out. So I now have a 3-disk RAID 0. It's considerably faster on boot up, about 1 minute after POST.

    It's also considerably faster, almost linearly, with my IO-bound processing. I'm quite impressed.

    I have been considering purchasing a RAM drive, which uses DDR / DDR2 as a volatile hard drive. Has anyone had any experience with this? I have seen it has throughput twice as fast as the fastest raptors.

    That alone wouldn't make it worth it IMO, but I was wondering what other people had thought.

    Also, I remember DOS had a utility called RAMDISK, is it possible to do something like this under Vista? I looked it up and it looks complicated... Any experience?
    hasafraggin shizigishin oppashigger...

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    Just add more memory and create software ramdisks. That way you won't be limited by SATA bandwidth. I get about 1GB/s from ramdisks.

    It's certainly possible to create ramdisks under modern OSes. I'm not sure how to do that on Windows, though.

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    Linguistic Engineer... doubleanti's Avatar
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    I've thought about ramdisks, but the loading time would defeat the purpose of not just loading the data directly to RAM via my computer.

    I'm enjoying the speedy throughput of a 3-disk raid 0 at the moment, I get throughputs of 70 mb/s+. =p

    Except, now I want to put a fourth HD (for media), and my board only has four sata ports (not something I ever thought I'd need more off back when...) Can someone recommend a sata raid card, or... should I wait until next round of AMD procs and wait wait wait for a 12 core, 16 gb ddr3 monster?
    hasafraggin shizigishin oppashigger...

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    Quote Originally Posted by doubleanti View Post
    I'm enjoying the speedy throughput of a 3-disk raid 0 at the moment, I get throughputs of 70 mb/s+. =p
    70MB/s... That's all?
    Get some Seagate Barraducas. I was getting 98.9MB/s without any HD or Volume cache enabled and 262.8MB/s with both caches enabled.
    "I am probably the laziest programmer on the planet, a fact with which anyone who has ever seen my code will agree." - esbo, 11/15/2008

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    Hmm... I get 100MB/s from my single $70 harddrive...

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    Quote Originally Posted by cpjust View Post
    70MB/s... That's all?
    Get some Seagate Barraducas. I was getting 98.9MB/s without any HD or Volume cache enabled and 262.8MB/s with both caches enabled.
    That's what I have! I just loved the name. 500mb for $50. There is a catch here tho: my drive has been fine, but there was a bad thing that happened a few months ago with them; if you google "Seagate Barracuda firmware problem" you may find some stuff. I think part of the complication was people who didn't have the problem installed the firmware anyway just to be safe and it made the drives worse. Probably the problem is fixed if you buy them now.

    I have not tested it for speed but the SATA cables are nice. I actually have most of it empty. Would there be any point to splitting the drive in half and running RAID that way (can you?) IE, so I could have one 250 mg RAID 1 drive? Then if there is corruption on half the disk it would be still be okay...probably that is silly as most significant hardware problems would be a total disk failure.
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    Would there be any point to splitting the drive in half and running RAID that way (can you?)
    You certainly can. With Linux software RAID, you can set up RAIDs between any partitions (as opposed to disks). I even tried a RAID-0 between a harddrive partition and a USB flash drive (worked, but not any faster =P).

    As for whether there is a point...

    At the very least, write speed will suffer greatly (everything needs to be written twice, on the same drive, so not at the same time). And it's possible that you will wear out your drive faster (a lot more seeking).

    [edit]
    I guess it helps against bad sectors, but I wouldn't personally do it, given the huge performance penalty (for random writes, seek time would double, too), and possibility of reducing the life of the HD.
    [/edit]
    Last edited by cyberfish; 06-10-2009 at 09:40 PM.

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    Quote Originally Posted by MK27 View Post
    I have not tested it for speed but the SATA cables are nice. I actually have most of it empty. Would there be any point to splitting the drive in half and running RAID that way (can you?) IE, so I could have one 250 mg RAID 1 drive? Then if there is corruption on half the disk it would be still be okay...probably that is silly as most significant hardware problems would be a total disk failure.
    That's what I do with my RAID. I had the Windows partition set to RAID 0 and the data partition set to RAID 5. Although now I set them both to RAID 5 after experiencing the pain of having a drive die.
    "I am probably the laziest programmer on the planet, a fact with which anyone who has ever seen my code will agree." - esbo, 11/15/2008

    "the internet is a scary place to be thats why i dont use it much." - billet, 03/17/2010

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    I think he meant running an RAID from two partitions on the same drive.

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