RAID Questions

Discussion in 'Mac Accessories' started by bleimone, Feb 5, 2007.

  1. bleimone macrumors member

    Joined:
    Jan 6, 2004
    #1
    Hello,

    I just sold my eMac and Upgraded to an iMac that has a 250GB hard drive. I have an external 120 firewire as well. I would like to have some advice on how to have the best back up set up.

    Previously, having the eMac, there was no problem backing up the entire hard drive because it was smaller than my whole external, but now its the other way around.

    I just started reading some information about RAID. Would you suggest for a regular uses to use RAID or just some back up program.

    Am I able to partition the 250 drive on the iMac without loosing anything to make one RAID so each has 125?

    Is it possible to just back up certain sections with RAID having an external 120?

    Thanks for your help.
     
  2. CanadaRAM macrumors G5

    CanadaRAM

    Joined:
    Oct 11, 2004
    Location:
    On the Left Coast - Victoria BC Canada
    #2
    Simple: Don't do RAID. It does little or nothing for you.

    Especially don't do RAID mixing internal and external drives.

    You are far better to set up a scheduled backup of data with Superduper or Silverkeeper or another backup program. You don't have to back up literally everything, mainly just your data (you can always reinstall applications from their CDs) so your backup drive does not necessarily have to be the same size as your original.

    Backing up to another partition on the same drive is of limited use. If the drive breaks down, you have lost both your backup and your original.
     
  3. eenu macrumors 65816

    eenu

    Joined:
    Aug 11, 2006
    Location:
    Manchester, UK
    #3
    Sorry i strongly disagree and think that is a huge sweeping statement!

    The rest of your post i agree with however.
     
  4. CanadaRAM macrumors G5

    CanadaRAM

    Joined:
    Oct 11, 2004
    Location:
    On the Left Coast - Victoria BC Canada
    #4
    RAID 0 (striping) has been tested and shown, under the majority of single user desktop uses, to have no improvement in speed (may even be slower), but a huge increase in risk of losing data. (See www.storagereview.com. It'a all about the usage patterns.)

    RAID 1 (mirroring) is a valid concept, but the OP is talking as if RAID is a replacement for doing backup, which it is not. The problem with mirroring is, if you accidentally delete a file, or save over top of it with bad data, or have a crash / virus / whatever that corrupts data, the damage is done to the mirror copy instantaneously, as well as to the master.

    Then, the OP has an iMac, with one internal drive. RAID of any sort between an internal drive and an external drive that can be turned off, or disconnected, is risky, and the lower speed of the Firewire bus would slow down write operations. And if you were to make an Apple RAID set of the external and internal drive, it would be limited to the size of the smaller of the 2 drives.

    So for the OP, RAID of any kind is really a non-starter.

    RAID 0 should not be considered by anyone unless they are setting up a server, or are doing intense digital video or audio, and only then in conjunction with a solid backup plan or additional mirroring (0+1 for example)

    RAID 1 is a reasonable idea if you need extra redundancy against single-drive failure, for machines with more than one internal drive capability, or in an external drive array. Again, only to be considered where there is also a solid data backup plan in place.
     
  5. eenu macrumors 65816

    eenu

    Joined:
    Aug 11, 2006
    Location:
    Manchester, UK
    #5
    actually my advice to the user would be to buy a raid enclosure and stick 2 x 250GB Drives in there and do a RAID 1 config and back up his or her entire drive to it.

    Sorry i may have understood you i thought you were basically saying RAID would never be valid or useful for the OP.
     
  6. leemason macrumors newbie

    Joined:
    Feb 24, 2007
    Location:
    London
    #6
    RAID 1 is very good for protecting against hard disk failure. If one disk fails then the other will keep you going. Even better is to use RAID 1 with a hot swap disk which will immediately cut in if you have a hard disk failure and rebuild the RAID set on the new disk. This keeps your RAID1 protection even if a disk fails, giving you time to replace it.

    RAID1 can improve performance for reads very slightly (because reads are distributed across the two disks and whichever disk gets to the data first sends it back to the system). By the same token it can slow down writes for the same reason (both disks need to write the data back). The impact on writes is reduced by cache on RAID controllers.

    RAID1 does not protect against data corruption, accidental deletion, or operator error. You still need to take backups to protect against these (which are probably much more likely than disk failure). You could use an external disk for this type of backup. However, make sure that you have some way to "offsite" your backups as well in case of disaster.
     
  7. nemenyi@mac.com macrumors newbie

    Joined:
    Apr 8, 2007
    #7
    My Raid Problem. Enyone can help?

    Hi Guys,

    I have 2x500 Gig HD (Bay0 and Bay1) set as stripped Raid (0) The total capacity is 1 T
    I purchased 2 more 500 Gig HD and placed them in Bay 3 and 4. I wanted to set them up as a 1T mirror reflecting the original 1T stripped HDs I have had.
    But it does not work like, I wanted. I can set them up as mirror (Raid1) but then they mirror each other (Bay 3 and 4 and not Bay 0 and 1) and the total capacity will be 500 Gig each. Before I became an Apple user I could set up in the windows environment 2 HDs as Raid 0 (stripped) and another 2 Hds as mirror (stripped and mirroring the first stripped duo).
    I can not do this with my MACPro. I guess the problem is my lack of experience in the MAC world. Anyone for the rescue? I could take responses on my email (nemenyi@nemenyi.net) as well. THX.
     
  8. CanadaRAM macrumors G5

    CanadaRAM

    Joined:
    Oct 11, 2004
    Location:
    On the Left Coast - Victoria BC Canada
    #8
    You are looking to set up a RAID 10 (or 1+0)

    http://docs.info.apple.com/article.html?artnum=304377
     
  9. nemenyi@mac.com macrumors newbie

    Joined:
    Apr 8, 2007
    #9
    Raid Question

    Thanx for your help. This are the reccomended steps:

    1,Create three blank RAID schemes in Disk Utility (two mirror and one stripe, or two stripe and one mirror).
    2,Drag two of the drives to the first set.
    3,Drag the other two drives to the second set.
    4Then in the RAID window drag the first and second set into the third scheme.
    Click Create.

    But I have the original 2 disks given as Raid 0 in the bay 0, and 1
    I purchased 2 more and created the as another Raid 0 (stripped pair as the original 2)
    When I tried to follow your hint ans created a third container (not real Hd but virtual) and dropped the working disk pair (bay 0 and 1 stripped) and also the second added disk par (bay 3 and 4 stripped but empty) the system took it in the Raid window until I hit the create button. Then I got the following error note: Creating Raid set failed - could not unmount disk.

    At that point I got stuck. Where did I make the mistake?
    Thx.
     

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