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two scratch discs, set-up

469 Views 7 Replies Latest reply: Feb 4, 2013 7:35 PM by Keith Worsley-Brown RSS
Keith Worsley-Brown Level 1 Level 1 (20 points)
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Feb 1, 2013 10:01 AM

Having just lost 2 years of media files for FCE projects (due to the failure of the single external HD I set as a scratch disc,) I now have two external HDs.  (Three actually, but one is dedicated to Time Machine.)


I see that I can set them both as scratch discs in FCE, but the guy in the store said it might be better to have one set up as the FCE scratch disc, and the second one mirrored using RAID.  Does anyone have any advice on which is the preferable method please? 


How does FCE access the data if it is stored on two separate drives, or don't I need to be concerned about that?  I just want to be sure that I don't lose my projects again.  Thank you.  Keith

iMac, OS X Mountain Lion (10.8.2), have iMac27, use FCE and iMovie11
  • MartinR Level 6 Level 6 (14,560 points)
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    Feb 1, 2013 10:44 AM (in response to Keith Worsley-Brown)

    Hi Keith,


    A RAID mirror set (which consists of 2 physical drives) appears to the system as a single drive.  When you create the RAID mirror set, you will give the mirror set a name, which is then the drive name.   The RAID mirroring process automatically duplicates the same data on both physical drives invisibly & simultaneously.  If you wanted to use the RAID mirror set as your FCE scratch disk, you would only have one FCE scratch disk, not two.


    I would not advise using two separate external drives as a RAID mirror set.  The only way to do this would be through software, specifically in Disk Utility.  This is (imho) a much riskier RAID mirror than having a hardware-based RAID mirror (a 2-drive  enclosure where the mirroring is all hardware based in the enclosure).


    Also, RAID mirroring is not a substitute for backup or archiving.  Yes, it protects against a single physical drive going bad, but the set is online, it is not offline backup.  And more data gets destroyed through user error or software error than by physical drives failing.  So, separate, external backup is equally if not more important than having a RAID mirror.

  • MartinR Level 6 Level 6 (14,560 points)
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    Feb 1, 2013 10:53 AM (in response to Keith Worsley-Brown)

    Using 2 drives as FCE scratch disks does not provide any better protection against data loss than only having 1 drive.  FCE would use the first scratch disk until it's full, and then start using the second scratch disk.  There would be no backup.


    My advice is to use one drive as your FCE scratch disk and the second drive as backup.  You could manually copy your clips & project files to the backup drive, or use something like CarbonCopyCloner to automate the backups.


    (And by backup, I am not suggesting the use of Time Machine as your backup.  TM is a great thing, but it's still an online drive and in my book that's not an effective backup plan.  True backup needs to be offline except for times you are actually doing  backup & restore operations.)

  • MartinR Level 6 Level 6 (14,560 points)
    Currently Being Moderated
    Feb 1, 2013 2:10 PM (in response to Keith Worsley-Brown)

    You could do one of the following:


    • Use the Finder to periodically and manually copy a) the entire Final Cut Express Documents folder or b) everything except the Render Files or from your scratch drive to your backup drive.  The problem with this method is you end up manually copying everything every time.   Of course, you could get away with copying your source media clips just the first time you back up manually, but then you have to keep track of everything yourself because you may add more clips as you go along.
    • Use CarbonCopyCloner (free) or a similar utility to automate the backup/synchronization process.  It takes a little learning & practice to set up the first time but afterwards you can schedule CCC to run periodically, or on demand.  Doing it this way you can set parameters on how to handle duplicate files, files that have changed, exclude certain folders (eg the Render Files folder) etc. from the backup and other things.


    There are additioanl possibilities but these seem to be the simplest to me.


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