RAID 5 with 4 1TB drives and RAID card

Discussion in 'Mac Pro' started by kittiyut, Jan 17, 2008.

  1. kittiyut macrumors regular

    kittiyut

    Joined:
    Oct 28, 2007
    #1
    I did a search on this but couldn't find anything, so here's my question:

    I'm getting the new Mac Pro 8 core 3.2 with the RAID card (getting the
    4 Seagate 1TB 7200.11 drives separately - why pay APPLE that much?)
    I want to do RAID 5 for both redundancy and performance and not lose
    too much capacity (like you do in RAID 0+1) what would you guys do;

    - use all 4 drives in RAID 5
    - use 3 in RAID 5 and 1 for the OS (does this make sense?)
    for this option, there's no redundancy for the lone drive.

    what do you experts out there think? :confused::confused:

    KK
     
  2. tersono macrumors 68000

    tersono

    Joined:
    Jan 18, 2005
    Location:
    UK
    #2
    I'm a great fan of RAID 5 + hot spare (which is how I usually configure servers), but under the circumstances, that's not an option here - I'd go for 4 drives in the array.
     
  3. kittiyut thread starter macrumors regular

    kittiyut

    Joined:
    Oct 28, 2007
    #3
    And your reason is?
     
  4. Toups macrumors regular

    Joined:
    Nov 23, 2007
    #4
    Place them into a single array, then create a seperate partition for OS so that you have the logical seperation and still maintain the performance and fault tolerance of RAID 5.

    Do NOT forget to backup important data, as RAID is only tolerant of drive faults, and does not cover file corruption or unintended deletes/user errors.
     
  5. Brutus Rex macrumors newbie

    Joined:
    Jan 13, 2008
    #5
    whats the volume size

    if he puts all 4 1tb drives into the raid 5 array, what is the volume size? how many drives can fail and still be okay?
     
  6. Rick Here macrumors member

    Joined:
    Oct 9, 2007
    #6
    The volume will be roughly 3/4 of the entire 4 drives or 3TB since one drive will used for the parity to protect the array.
     
  7. 9Charms macrumors regular

    9Charms

    Joined:
    May 19, 2006
    Location:
    Vancouver, BC
    #7
    I would put 3 drives in the RAID 5 and all data there should be safe against drive failure. I would then use the 1 drive that isn't in the RAID as your system drive and have Time Machine back it up to the RAID array. In a RAID 5, one drive is always used for redundancy so you would lose the capacity of that drive... You might able to stick a drive in the 2nd optical drive bay...
     
  8. kittiyut thread starter macrumors regular

    kittiyut

    Joined:
    Oct 28, 2007
    #8
    Wrong. RAID 5 distributes the parity across the array, not just in one
    particular drive - that's RAID 4. However, you are correct that the amount
    of space will be 3TB since all 4 drives are the same capacity (1TB) ;)
     
  9. 9Charms macrumors regular

    9Charms

    Joined:
    May 19, 2006
    Location:
    Vancouver, BC
    #9
    Yes. For example, my Athlon PC is running a RAID 5 array with 7 x 250 GB HDD, but I only have the usable capacity of 6 x 250 GB. It's always the number of drives less 1. ANY drive can fail and the array would be fine, but no longer redundant. (RAID 6 capacity is number of drives less 2)
     
  10. Rick Here macrumors member

    Joined:
    Oct 9, 2007
    #10
    Excuse Me ! I meant one drive capacity. Yes the parity is distributed across the entire set of drives.
     
  11. 65StangBoy macrumors member

    Joined:
    Dec 29, 2007
    #11
    I have my 4 750's in a RAID5. Within that array I have two volumes. One 300GB volume for the OS and Applications and the rest of the 1.5TB as a storage volume which also has my home directories. I accidentally wiped out my OS volume and it was really nice having my home directory somewhere else.
     
  12. MacRoom macrumors member

    Joined:
    Oct 25, 2007
    #12
    I Was Told By An Apple Expert At MacWorld To Only Raid 5 Three Drives, Not Boot Drive

    I got my four 1TB Seagate drives on sale at Fry's the weekend before MacWorld for $270 each. I'm getting the same 3.2GHz Mac Pro you are with the Raid card. An expert at the Mac Pro part of the Apple booth told me NOT to Raid 5 all four. He said to Raid 5 three beyond the boot drive. I plan to follow his advice.

    Yes one PATA drive easily fits under the optical so a total of 5 drives are possible inside.
     
  13. kittiyut thread starter macrumors regular

    kittiyut

    Joined:
    Oct 28, 2007
    #13
    Wow, how did you "accidentally" wipe it all out? Mind sharing so we don't make the same mistake??:rolleyes:
     
  14. 65StangBoy macrumors member

    Joined:
    Dec 29, 2007
    #14
    Yeah, it was stupid but atleast I learned something. I was trying to get GRUB to boot my Windows XP partition and was having problems so I had to wipe out the MBR. I read somewhere that it wouldn't be a problem to do that since OSX didn't use that part of the drive. WRONG!!! Wiped it and all of a sudden my OS volume was trashed. No biggie since my home directory was on another volume. Just had to reinstall the OS and my applications. Lesson learned.
     
  15. 9Charms macrumors regular

    9Charms

    Joined:
    May 19, 2006
    Location:
    Vancouver, BC
    #15
    Really? What reasons does he give? Why 3?

    I'd be tempted to RAID as many drives as possible to reduce the wasted overhead. However, I definitely would not RAID my boot drive or scratch drive as it would slow the computer down and become a bottleneck.
     
  16. 65StangBoy macrumors member

    Joined:
    Dec 29, 2007
    #16
    I can't think of any reason why they would suggest only running a three drive RAID5. The more spindles you have in your RAID5, the better the performance.
     

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