Mac Pro RAID Card - No Battery?

Discussion in 'Mac Pro' started by Hally231, Apr 1, 2011.

  1. Hally231 macrumors member

    Joined:
    Oct 25, 2010
    #1
    I have just installed a mac pro raid card in my 07 Mac Pro and the battery comes out as 'faulted' and wont really charge. A new battery is about £80 and will need 72 hours of charging and then gets reconditioned once every 3 months. Im only using the raid card for personal use - from what i understand the battery protects the data when the power goes down.

    My question is that do you think its worth getting the a new battery or just use the raid card with a faulty one?

    If i use the faulty battery will it still need to be reconditioned?

    Sorry - i am new to the world of RAID backup

    Peace x
     
  2. Transporteur macrumors 68030

    Joined:
    Nov 30, 2008
    Location:
    UK
    #2
    If you've got an UPS in place, the RAID card battery is redundant, so you'd be fine without it.
    It also depends on which type of array you run. For a parity based array (5/6), I'd use a battery backup unit (BBU), otherwise you might lose data in case of a power out. That can always happen, though, which is why a UPS is advisable in every case.

    Ups, RAID is NO backup, no matter which type of array you run. Performance and/or availability come into mind, but not backup.
     
  3. Hally231 thread starter macrumors member

    Joined:
    Oct 25, 2010
    #3
    Thanks - i dont have a UPS atm. Could you please explain a bit more about the backup battery and cache?

    So if i have a powercut - what should the battery do?

    I admit im a complete noob at RAID but really interrested!!!
     
  4. Transporteur macrumors 68030

    Joined:
    Nov 30, 2008
    Location:
    UK
    #4
    The battery ensures that the data that is not yet written to the discs is hold in the controllers cache till the power is restored. It then gets written to the discs.

    Personally, I'd rather invest in a UPS for the whole system (they aren't that expensive any more), than the 80 quid for the RAID BBU.

    Anyhow, what RAID level are you running? Maybe you don't need the hardware RAID card in the first place.
     
  5. Hally231 thread starter macrumors member

    Joined:
    Oct 25, 2010
    #5
    Well i would like to create the raid that allows 3 hard drives to combine as 1 and if 1 hard drive fails and the others still function and will be able to repair.
     
  6. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #6
    This would be RAID 5. It needs another disk to rebuild though, and if you don't run a hot spare, you must replace the faulty disk manually in order for a rebuild to begin, so keep this in mind. ;)

    As per the battery, it keeps the cache active when there's no power to the card (retains data until the battery's charge runs out). But if the file to be written is larger than the cache, or power goes down during the process that generates the write data (incomplete), then you'll very likely end up with corruption (definite on a file that's partially stored in cache, the rest in system memory; automatic resume can re-perform work in some cases, but it's not a good idea to rely on this). This is why a UPS is better if you only have one or the other.

    Ideally, you run both the card's battery + UPS (get a pure sine wave output unit with as much VA as you can manage <1500VA is usually the max you can go on a typical household socket = no need for an electrician>, as the run time reduces as the batteries wear).

    Hope this helps. :)

    Refurbished work just as well as new, and can be had cheaper (can be had for ~$250 - 300USD this way).
     
  7. Hally231 thread starter macrumors member

    Joined:
    Oct 25, 2010
    #7
    Thanks..

    Thanks, im getting a better understanding now.

    Does cache get written to the disks most of the time or is it only when you add new files to be 'backed up'?

    Sorry about my lack of knowledge - ive stepped up to RAID from basic USB Hard drive backup.
     
  8. nanofrog macrumors G4

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    May 6, 2008
    #8
    The cache installed on the RAID card is only used for writes (any write that's handled by the card).
     
  9. bizzle macrumors 6502a

    Joined:
    Jun 29, 2008
    #9
    The old Apple RAID card (the one you are using) is notoriously awful and the batteries and the cards themselves have very high failure rates. I've replaced tons of them over the years.
     
  10. Hally231 thread starter macrumors member

    Joined:
    Oct 25, 2010
    #10
    okay

    Yes i have just read about the cards faults - i which i searched the forums before purchase!

    How long roughly do brand new batteries last for as i may buy one?

    And for how long does the raid card actually write cache to the drives for? Im going to set up a RAID 5 array with 3 hard drives 2tb each - this sound alright?

    Thanks
     
  11. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #11
    This depends on the number and size of the files to be written.

    Completed information <process that's created it is finished> but still waiting to be written, is first stored in RAM. It's then moved in the RAID card's cache (also RAM, but located on the card and separate from the system's pool), and finally transferred to the disk. So it's done when all the write processes are completed to the disks (until this point, there will be data stored in the card's cache).
     
  12. Hally231 thread starter macrumors member

    Joined:
    Oct 25, 2010
    #12
    cool

    Okay thanks, do you know how long brand new raid card batteries last for? I.e 6 months or something.

    Thanks
     
  13. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #13
    On that card, I don't know (they're so bad, I recommended clients replace them with a better card). From what's been posted here however, it doesn't appear to be long at all, so 6 months may be as good as it gets. :eek:

    Generally speaking however, it depends on a few factors, notably the type of battery tech used (i.e. NiCad, NiMh, LiIon, ...). Without the details, I've seen as short as 1 year, but as long as 3 years.
     

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