Help me out with RAID 5

Discussion in 'OT Technology' started by turbodeuce, Mar 5, 2007.

  1. turbodeuce

    turbodeuce ....................

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    So I am looking to build a new rig with a massive amount of storage with some redundancy. I preferably want ~2gb of storage, mostly for digital media. I am looking at doing either a 4 port card with 4x750gb seagate 7200.10 would give me 2.25tb or an 8 port card with 5x500gb 7200.10 would give me 2tb, correct? I am leaning towards the 500gb drives since they are now below $150 and the 750s are still around $300. I don't have a set budget, but the cheaper the better of course.

    Can anyone point me towards some raid card model/brands to look at? Looks like ebay is the cheapest for the cards. My friend told me to look at at the Highpoints.

    How big of a difference am I going to see with PCIe 1x vs 4x? Everything will be local for right now, but may be streamed in the future.

    What the hell is XOR?

    Comments / suggestions?
     
  2. P07r0457

    P07r0457 New Member

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    XOR is a type of logic opperand:
    http://www.sr5tech.com/raid5.htm

    The rule for RAID5 available storage capacity is (assuming all drives are the same size) available_capacity = Size_of_drive * (Number_of_drives - 1).

    What's your price range for the card? That will be a big factor.
     
  3. turbodeuce

    turbodeuce ....................

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    Well the 8 port highpoints with pcie 4x were under $300 on ebay. I don't really have a price range, but don't know what the more expensive ones give me... edujamacate me.
     
  4. P07r0457

    P07r0457 New Member

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    you want sata, pata, or scsi?
     
  5. turbodeuce

    turbodeuce ....................

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  6. turbodeuce

    turbodeuce ....................

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    The power at my place is kinda f'd up and does go out from time to time. Should I be looking at a controller that has nvram?
     
  7. P07r0457

    P07r0457 New Member

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    nvram and battery backup are a must to avoid data corruption. Nvram helps sync the writing of the actual data and parity information... Likewise, a battery backup helps the controller finish before shutting down.

    However, you should never have a desktop machine without a decent UPS, anyway, imho.
     
  8. P07r0457

    P07r0457 New Member

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  9. turbodeuce

    turbodeuce ....................

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    thanks for the links.

    Now I'm really confused, so ideally I should have a raid controller with nvram (cache memory is the same right?) that supports battery back up and a separate battery back up card and an external UPS?

    The 3ware and LSI card you linked are more expensive because of the onboard ram, right? What else am I paying for? Do they already include battery back up or do I need to purchase something separate?
     
  10. P07r0457

    P07r0457 New Member

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    well, if you have a UPS running the machine, you're okay 98% of the time. The exception would be if there is a hardware crash and the system just restarts or shuts off. Another exception is a failed PSU.

    In terms of price, the 3Ware and LSI are going to be more money because of the brand. They're the ferrari of the category. The HighPoint is like a mazda. Personally, I like the 3ware. LSI is also good. The 3Ware has 256MB of 533MHz DDR2. The LSI has 128MB or 333MHz DDR. The HighPoint uses system memory. I've had mixed results with HighPoint, but I hear their drivers are getting better?
     
  11. turbodeuce

    turbodeuce ....................

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    Sorry for the ignorance, but is the ram on the cards is the same as nvram, besides security against data corruption it just doesn't bog down on system memory? The ram would only come into play when writing to the disk or rebuilding the array? Most of the files will be written to the array when the computer isn't doing other things, so should I be fine with the Highpoint card and a UPS?
     
  12. P07r0457

    P07r0457 New Member

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    nvram is not the same as ddr. NV stands for "non-volatile". NVRAM is used when data needs to be preseved after a power outage. DDR requires power to retain data. NVRAM is typically used to store BIOS and config information... Things that need to be changable, but may not change often, and write speed is not important. Most controllers use NVRAM to store their configuration. Some store it on the hdd, however.

    As for dedicated cache memory vs system memory, it's a big difference, imo. Using system memory is going to have to go over the bus, and through the memory controller. Then it takes away from main system memory (like an integrated vid card would). Lame. Dedicated cache memory is faster. This helps 98% of the time with better performance. It can also make that difference the other 2% commiting data to the disk more quickly than sharing system memory.

    Overall, the HighPoint+UPS is okay for most people. The other cards are better. Whether or not they're worth the extra $ is a decision you need to make.
     
  13. Peyomp

    Peyomp New Member

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    I know I'm hyping ZFS and all but... you do not need a raid card to do RAID-Z with ZFS, and it will be more reliable than hardware RAID 5. That makes sense in your application, where its you paying for this.
     
  14. P07r0457

    P07r0457 New Member

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    I disagree. Real-world, I think hardware RAID is more reliable than software RAID. Performance is also better.
     
  15. Peyomp

    Peyomp New Member

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    I completely agree. But Real-world RAID-Z should be more reliable than both.
     
    Last edited: Mar 5, 2007
  16. P07r0457

    P07r0457 New Member

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    you're saying that a product that isn't even an ALPHA release is going to be more reliable real-world than hardware products that have been PROVEN for years?

    You know I like ya, but put down the pipe!
     
  17. deusexaethera

    deusexaethera OT Supporter

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    It would be cool if SMS would make a hardware-based RAID-Z controller, to satisfy people who don't want to waste CPU power doing a job has had discrete hardware available for years now.
     
  18. AlcoLOLic

    AlcoLOLic New Member

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    So, let me get this straight...when 500GB HDs are ~$150 each, controller cards are around ~$249 each, and you want ~2TB of storage...that's $849 before shipping, taxes, and you're not even done buying all the hardware...not to mention configuration tasks.

    I must be a Buffalo sackrider...because in this situation, a 2.0TB Terastation is around $849 now without having to screw with any of that. Raid5 capability is already there. Deploy instantly and go, gigabit functionality.
     
  19. keleko

    keleko yes, he is

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    2nded
     
  20. keleko

    keleko yes, he is

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  21. P07r0457

    P07r0457 New Member

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    buffalo :mamoru:


    guys, he's talking mercedes benz s-class... you just suggested dodge neon.
     
  22. Peyomp

    Peyomp New Member

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    RAID-Z isn't Alpha. Its not Beta. Its production. It already went through those earlier cycles. Admittedly, is still new as a production filesystem. But if it works as advertised, and I have found that it does, then it is more reliable than both software raid, and hardware RAID-5, just like I said it is. Should he deploy it in a production environment? Maybe. I have. But at home? Absolutely no sweat. It works. There isn't any question about this. There remain certain self-tuning capabilities that aren't complete, but the basic functionality is flawless.

    ZFS is good at home, just like its good where I use it: where you want to minimize hardware costs, but still have reliable storage.
     
    Last edited: Mar 5, 2007
  23. Peyomp

    Peyomp New Member

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    RAID-Z acts atomically with stock hardware. The entire point is that it is more intelligent than hardware solutions. I'm not saying I would object to an on-board controller, but in practice I don't think this would see much benefit. ZFS can use a lot of ram during big filesystem operations, so you would have to have a lot of ram for the card, which as well be a single core, anyway.
     
  24. keleko

    keleko yes, he is

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    atomically? :noes:

    i don't want no nukes near my data! :nono:
     
  25. Peyomp

    Peyomp New Member

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    Yes you do. Atomic writes make your data nuclear super duper.
     

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