RAID 5 vs RAID 10 (or 0+1) for media storage

Discussion in 'OT Technology' started by o2, Apr 22, 2007.

  1. o2

    o2 Witty Title Here OT Supporter

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    Im building a home theater PC, to store a lot of videos, music, etc. Im going with a multi-HD setup, so I was wondering what would be the best idea?

    I plan to have about 1.5-2TB of storage (probably 500GB drives, since they are cheap). In case of HD failure Id replace it within a day or 2. So with 5x500GB drives I'd be able to do the RAID5 setup that will have 2TB of storage, and it will be able to survive in case of a single HD failure? Is that right?

    What about the read/write speed? Is it the same on RAID5 as RAID10? I know on a media PC it doesnt matter, but I currently run RAID 0+1 on my main PC, and if I convert to RAID5, I'll have an extra 320GB of space.
     
    Last edited: Apr 22, 2007
  2. P07r0457

    P07r0457 New Member

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    RAID 0+1 is shitty. Basically you take a Stripe Array, and then mirror it. This means that you get N*C/2 storage space, where N is the number of drives, and C is their capacity.

    RAID 5 creates parity information and distributes it among the drives. This means you get (N-1)*C storage space, where N is the number of drives, and C is their capacity.

    Let's put this in perspective:

    4 Drives of 500GB each:
    RAID 0+1: 4*500/2 = 2000/2 = 1,000 GB
    RAID 5: (4-1)*500 = 3*500 = 1,500 GB

    So you store MORE with RAID5. It's also quicker to rebuild and more robust. How many enterprises run RAID0+1? Few. How many run RAID5? Lots.
     
  3. deusexaethera

    deusexaethera OT Supporter

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    RAID 0+1 gives you RAID-0 speed with RAID-1 protection, but RAID-1 protection is overkill except in two-disk arrays (where there is no other option) or in extremely critical applications (like military FOB servers). The choice that will make any difference to you is: RAID-1, RAID-3, or RAID-5.

    - RAID-1 is only practical if you have only two disks, as previously stated, but when you only have two disks, it's your only viable option.

    - RAID-3 stores all the backup data on a single disk at the end of the array
    , which means that large disk writes can bottleneck and slow down because any modification to any of the disks has to be reflected on the one single backup disk -- however, if you're going to be doing much more reading than writing, RAID-3 also reads data faster because it doesn't have to skip over blocks of backup data scattered across all of the disks.

    - RAID-5 is a more balanced system that scatters backup data across all of the disks in the array. This slows down reads a bit because it has to skip over blocks of backup data no matter which disk it happens to be reading from at any given moment -- but it also means that writing data won't cause bottlenecks because the backup data that needs to be updated isn't all on one disk.

    So, in summary:

    Two disks? Use RAID-1.
    Running a database? Use RAID-5.
    Storing and reading data that doesn't change often? Use RAID-3.
    Invading a foreign country? Use RAID 10.
     
  4. P07r0457

    P07r0457 New Member

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    I would recommend RAID5 even for normal machines looking for a RAID solution. Installing windows has become a psudeo-benchmark for me, and it is rediculously quick on a RAID5 system.
     
  5. keleko

    keleko yes, he is

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    http://www.raid.com/04_00.html

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    [​IMG] [FONT=arial, helvetica]Click on the diagram to see RAID 0 in action[/FONT] [​IMG] [​IMG]
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    [FONT=arial, helvetica] RAID Level 0 requires a minimum of 2 drives to implement
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    [FONT=arial, helvetica] RAID 0 implements a striped disk array, the data is broken down into blocks and each block is written to a separate disk drive
    [/FONT] [FONT=arial, helvetica] I/O performance is greatly improved by spreading the I/O load across many channels and drives
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    [FONT=arial, helvetica] Best performance is achieved when data is striped across multiple controllers with only one drive per controller
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    [FONT=arial, helvetica] No parity calculation overhead is involved
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    [FONT=arial, helvetica] Very simple design
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    [FONT=arial, helvetica] Easy to implement
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    [FONT=arial, helvetica] Not a "True" RAID because it is NOT fault-tolerant
    [/FONT] [FONT=arial, helvetica] The failure of just one drive will result in all data in an array being lost
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    [FONT=arial, helvetica] Should never be used in mission critical environments
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  6. o2

    o2 Witty Title Here OT Supporter

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    What about the write/read difference between RAID10 (or 0+1) and RAID5? How much slower is RAID 5?
     
  7. keleko

    keleko yes, he is

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    [​IMG]
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    [FONT=arial, helvetica] RAID Level 10 requires a minimum of 4 drives to implement
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    [FONT=arial, helvetica] RAID 10 is implemented as a striped array whose segments are RAID 1 arrays
    [/FONT] [FONT=arial, helvetica] RAID 10 has the same fault tolerance as RAID level 1
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    [FONT=arial, helvetica] RAID 10 has the same overhead for fault-tolerance as mirroring alone
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    [FONT=arial, helvetica] High I/O rates are achieved by striping RAID 1 segments
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    [FONT=arial, helvetica] Under certain circumstances, RAID 10 array can sustain multiple simultaneous drive failures
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    [FONT=arial, helvetica] Excellent solution for sites that would have otherwise gone with RAID 1 but need some additional performance boost
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    [FONT=arial, helvetica] Very expensive / High overhead
    [/FONT] [FONT=arial, helvetica] All drives must move in parallel to proper track lowering sustained performance
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    [FONT=arial, helvetica] Very limited scalability at a very high inherent cost
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  8. keleko

    keleko yes, he is

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    [​IMG]
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    [FONT=arial, helvetica] The data block is subdivided ("striped") and written on the data disks. Stripe parity is generated on Writes, recorded on the parity disk and checked on Reads.
    [/FONT] [FONT=arial, helvetica] RAID Level 3 requires a minimum of 3 drives to implement
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    [FONT=arial, helvetica] Very high Read data transfer rate
    [/FONT] [FONT=arial, helvetica] Very high Write data transfer rate
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    [FONT=arial, helvetica] Disk failure has an insignificant impact on throughput
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    [FONT=arial, helvetica] Low ratio of ECC (Parity) disks to data disks means high efficiency
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    [FONT=arial, helvetica] Transaction rate equal to that of a single disk drive at best (if spindles are synchronized)
    [/FONT] [FONT=arial, helvetica] Controller design is fairly complex
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    [FONT=arial, helvetica] Very difficult and resource intensive to do as a "software" RAID
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  9. P07r0457

    P07r0457 New Member

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    but remember that RAID0+1 is *not* RAID10
     
  10. Doc Brown

    Doc Brown Don't make me make you my hobby

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    Then there is the other option. If it's strictly for media, you could do what I do.
    Drag each media file manually into both backup drives. I personally don't want every little thing that I do backed up to my hard drives.
    By doing it manually, I can keep the drives free of clutter.
     
  11. o2

    o2 Witty Title Here OT Supporter

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    Yeah, I dont really wanna copy it manually, and I want everything backed up.
     
  12. Doc Brown

    Doc Brown Don't make me make you my hobby

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    Depending on how frequently you add to the data base, you'd be surprised at how little work it takes.

    I keep a shortcut for two music/software drives in the toolbar. Anytime I want to add something in there, I just drop it into the proper folders.

    Another nice thing about that is that I can use a 73gb Raptor for the os, and then bigger drives for backup.

    I'm actually one drive from having music and software across two drives. And movies across two more. Five drives total.
    There's no way I could organize it that way with RAID.
     
  13. o2

    o2 Witty Title Here OT Supporter

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    Split the RAIDed drives into partitions. :dunno:

    Im gonna be constantly downloading new stuff. My new place has an unlimited 100mbit connection. :noes:
     
  14. Doc Brown

    Doc Brown Don't make me make you my hobby

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    Well I could see if you do quite a bit of changes it wouldn't be practical. But I've got 16 folders with sub folders on each of the two music/software drives. The movie drives are just movies, so I could do it on those but then I would never need to since I haven't been adding more than a movie or two a month lately.
     
  15. P07r0457

    P07r0457 New Member

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    Doc, that's a really silly idea. lets pretend you never suggested it, and just move on, okay?

    (understand I'm being nice here)
     
  16. 1999TL

    1999TL New Member

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    Sorry to hijack, but I was thinking about Doing a Raid 0 with two 36 gb Raptors. I want the speed b/c I'd be doing Video editing. I figure Ill just keep on doing Drive images and just copying the files that I need like I'm currently doing. Ok idea?
     
  17. P07r0457

    P07r0457 New Member

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    You arn't going to have appreciable speed increase with a RAID0 setup. In real-world applications, they simply are not effective.

    Not to mention, if you are working on a video, you obviously want to keep it! Thus, integrity is very important. RAID0 completely and blatantly disregards any attempt at integrity.

    Simply put: Do not use RAID0.
     
  18. deusexaethera

    deusexaethera OT Supporter

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    Two-drive RAID-0 is only a little faster than a three-drive RAID-3, and not nearly as safe. Don't even bother.
     
  19. deusexaethera

    deusexaethera OT Supporter

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    You've got two drives storing the same content already. Buck up and buy a controller to keep them synched automatically.
     
  20. deusexaethera

    deusexaethera OT Supporter

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    Eh...I forget, is RAID 10 the one where you have a RAID-0 comprised of several RAID-1's, and RAID 0+1 is where you have a RAID-1 comprised of two RAID-0's? I never really paid much attention to those setups because of the massive overhead they require.
     
  21. P07r0457

    P07r0457 New Member

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    RAID 10 is when you stripe a mirror.

    RAID 0+1 is when you mirror a stripe.


    Either way, not good, imo. I really think RAID5 is the best all-around setup. RAID3 is interesting, and I could see someone running it, but a proven controller is either going to support level-5 in addition to level-3 (then just run level-5), or if you do find a level-3-only card it probably isn't going to me much, if any cheaper than a level-5 card, so just go for RAID5.

    (note I say proven... This doesn't count some SYBA or [insert-shitty-brand-here] piece-of-shit card... We're talking 3ware, Adaptec, LSI-Logic, etc)
     
  22. Doc Brown

    Doc Brown Don't make me make you my hobby

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    If you saw my folder/hard drive setup you would understand.
     
  23. Doc Brown

    Doc Brown Don't make me make you my hobby

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    Well I'll cover this again, just in case I heard wrong the first time.

    From what I understand, you can't get RAID to backup selected items. Correct?
    I mean it's all or nothing, right?

    If that's the case, do not want.

    You just can't imagine the hours that went into organizing my drives just the way I want them.
    And I just don't see a way of maintaining that organization with a RAID setup. Not that I wouldn't want to. Hell, I would love it if I could.
     
  24. P07r0457

    P07r0457 New Member

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    wtf are you talking about?

    RAID is transparant to the OS. It looks like one big, simple, drive. What it does under the hood is no consequence. You can organize, move, delete, etc to your hearts content... It won't change the redundancy of the array.

    So you only have to organize ONE drive, the redundancy is auto-matic.


    In a simple RAID1 morror, you move file A from folder B to folder C and rename it to file C. The controller automatically performs these tasks concurrently on the mirrored drive.

    In the end, RAID1 provides a bit-for-bit copy.

    Other levels of RAID will do things differently, but the transparancey is universal. You don't have to go out of your way -- the controller provides redundancy automagically.
     
  25. Doc Brown

    Doc Brown Don't make me make you my hobby

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    Maybe I haven't been asking the right questions.

    Does every little detail on the main volume get reproduced on the backup volume?
     

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