Raid 1 - OS X setup using internal and external drives - how to recover or use?

Discussion in 'Mac Pro' started by Sean Dempsey, Sep 18, 2010.

  1. Sean Dempsey macrumors 68000

    Sean Dempsey

    Aug 7, 2006
    I am thinking of doing this:

    Tray 1: SSD boot/apps
    Tray 2: 1TB storage drive

    External 1 FW800: 1TB storage drive

    And then mirroring the TB drives with a OS X software Raid 1.

    But, if one drive crashes, is the other drive instantly usable? How do you separate or recover the "mirrored" drive in a Raid 1?

    Also, can you do a Raid 1 with a drive on an SATA, and then a FW800 with such different transfer speeds, will the FW800 drive be able to write as fast as the SATA one, or will the SATA one have to slow down?

    What is the best way to have an internal drive in the Mac Pro, and then have it real-time mirrored on an external? Or is this not possible.
  2. xper macrumors 6502


    Dec 15, 2005
    Sweden - Halmstad
    1TB drives are cheap, why not use 2 of them in raid 1? And maybe an external for backup if you are really afraid of loosing data
  3. Erendiox macrumors 6502a


    Oct 15, 2004
    Brooklyn NY
    I would not raid a FW800 drive and an internal SATA. It may work in theory, but I'm concerned you would have performance and reliability issues with it. The previous poster made a good suggestion on getting a second 1TB internal. That's what I would do.

    And aside from that, a drive that's separated from a RAID 1 is immediately available to use as a standalone drive. Getting that drive back into a RAID 1 once its been modified is less simple. I think you'd need to pick one drive to reformat and rebuild.
  4. Sean Dempsey thread starter macrumors 68000

    Sean Dempsey

    Aug 7, 2006
    That's what I thought I was doing? 1TB in the mac pro, 1TB in the external, mirrored in a 1TB Raid 1.

    I am just wondering what will happen with an internal SATA drive and an external FW800 drive (even if its a SATA drive) are mirrored, since the bus speeds of SATA are like 3000mbits, and FW800 is 800mbits.

    I know I could put a 1TB drive in 2 internal bays, and then mirror those, but I want my mirror to be external, but updated in real time.
  5. Sean Dempsey thread starter macrumors 68000

    Sean Dempsey

    Aug 7, 2006
    Can you make a raid1 off an existing drive without erasing the first drive, and just have the mirror update based on the "source" drive?

    Sounds like I'm better of just sticking to ChronoSync and SuperDuper for external backups. I know internal raids are easy, but I just like having my backups on external enclosures. Makes it easier to move, replace, and keeps it a little more separated from an electrical surge in the tower.
  6. Honumaui macrumors 6502a

    Apr 18, 2008
    it will go to the lowest speed ? you can do it but as said I would not ?

    I have heard some run into write problems cause the speed difference ?

    I almost always have my boots raid 1 cause I cant take any down time ?
    if one HDD dies it just keeps working ? a little bit ago you now have the option of selecting auto rebuild which is nice and never used to be their :)
    when I tested it I pulled a HDD out and did the rebuild I gave up and just took that remaining good HDD out and created a new raid 1 and cloned it over and I think it was quicker than waiting for the rebuild ?

    I am a big person to say TEST your system and KNOW how to get back and working when you are calm and in control since it happens for real its a freak situation :)
    two thoughts
    if the HDD is over 2 or more years old
    so anyway I also have the idea of if one dies ! I start over anyway ? cause if one fails the other is going to maybe ?
    if its under 2 years and or I can still get a duplicate HDD to replace I will :)

    the only way I would ever do what you are wanting is with eSATA ?
    jump your extra ports outside !
    my wifes is done like this onto a firmtek 2 bay case this is going to change though soon :)

    also I love time machine cause at least I can go back a hour ?

    also remember while its a mirror in raid 1 ? you delete a file you cant get it back :) so the only thing raid 1 IMHO does is protect you from a HDD failure and that is it !!!!

    on PCs I remember a program you could create a mirror ? never used it or no idea if it worked ? but I think its one of those start from scratch things anyway ?
  7. Erendiox macrumors 6502a


    Oct 15, 2004
    Brooklyn NY
    At first I was confused as to why, but now I understand. If you want an external backup of your storage drive then yes, you're better off using backup software like superduper or time machine. While a RAID 1 seems like it would do what you want it to, it's more than just a backup solution. A RAID disk is recognized as a single logical drive. Those drives need to be in sync, working together. FW800 and SATA are very different busses, and I think you will run into problems.
  8. nanofrog macrumors G4

    May 6, 2008
    I would not recommend this. The different busses can't sync properly, and it would be too unstable if it even works (not sure how robust the software component in OS X is; meaning is it limited to SATA only?, which I'd play it safe and presume is the case).

    In general, yes (presumes that the drives are connected to the same bus).

    Actually, once the array is created, it appears as a single disk, not separate disks. Once one of the disks fails, the other disk picks up, and keeps the system from being stalled or worse, dies (depends on whether or not the array is used or the OS or just data).

    I'm presuming you're looking to use a Mirror as an automatic backup solution. That's not what it's meant for. The reason being, if you make a mistake (i.e. accidentally delete a file), it's automatically performed on both members in the array = mistake is duplicated. So that deleted file would be gone. Period.

    That's why you need a backup system in place, no matter if it's a single disk or the most complex RAID system ever created.

    Absolutely. This can't be stressed enough, and it applies to both software and hardware implementations.

    MTBR (Mean Time Between Replacement) is another important aspect when dealing with RAID. I'm more accustomed to a 3 year cycle, but that's using enterprise grade drives, so if you meant for consumer models (possible with software implementations such as Disk Utility on the ICH), I'd agree that a 2 year cycle should be sufficient.

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