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  • El Capitan Software RAID size limit for FCPX backups

    Posted by Ted Irving on July 29, 2016 at 6:01 pm

    Just used Terminal to build a software RAID on my Mid 2010 Mac Pro tower running El Capitan. The external RAID is a SansDigital box with four drives that totals 9TB. Why does the terminal commands for building a RAID not utilize all of that space? The total size is now only 2TB. Can someone view the line commands and let me know what is wrong or are there other commands that will allow me to utilize the full 9TB of space?

    0: GUID_partition_scheme *3.0 TB disk5
    1: EFI EFI 209.7 MB disk5s1
    2: Apple_HFS RAID1 3.0 TB disk5s2
    /dev/disk6 (external, physical):
    0: GUID_partition_scheme *2.0 TB disk6
    1: EFI EFI 209.7 MB disk6s1
    2: Apple_HFS RAID2 2.0 TB disk6s2
    /dev/disk7 (external, physical):
    0: GUID_partition_scheme *2.0 TB disk7
    1: EFI EFI 209.7 MB disk7s1
    2: Apple_HFS RAID3 2.0 TB disk7s2
    /dev/disk8 (external, physical):
    0: GUID_partition_scheme *2.0 TB disk8
    1: EFI EFI 209.7 MB disk8s1
    2: Apple_HFS RAID4 2.0 TB disk8s2
    /dev/disk9 (external, physical):
    0: GUID_partition_scheme *2.0 TB disk9
    1: EFI EFI 209.7 MB disk9s1
    2: Apple_HFS SCRATCH 4. FANTOM D 2.0 TB disk9s2
    3: Apple_Boot Recovery HD 650.0 MB disk9s3
    TEDTVMACINTEL:~ FCP$ diskutil appleRAID create mirror Backup JHFS+ disk5s2 disk6s2 disk7s2 disk8s2
    Started RAID operation
    Unmounting proposed new member disk5s2
    Unmounting proposed new member disk6s2
    Unmounting proposed new member disk7s2
    Unmounting proposed new member disk8s2
    Adding a booter for the RAID partition disk5s2
    Adding a booter for the RAID partition disk6s2
    Adding a booter for the RAID partition disk7s2
    Adding a booter for the RAID partition disk8s2
    Creating a RAID set
    Bringing the RAID partitions online
    Waiting for the new RAID to spin up “2D90CDC9-D854-4C3E-B47E-8D5386F3020D”
    Initialized /dev/rdisk10 as a 2 TB case-insensitive HFS Plus volume with a 155648k journal
    Mounting disk
    Finished RAID operation

    Ted Irving
    ENG Cinematographer

    Craig Alan replied 5 years, 11 months ago 5 Members · 11 Replies
  • 11 Replies
  • Joe Marler

    July 29, 2016 at 9:46 pm

    I don’t have a quick answer but I notice you are trying to create a four-drive RAID-1 (mirror) set, where the drives are not the same size. I don’t have any experience with that, and I cannot find any AppleRAID documentation about how mirror sets would work with different-size size drives, or how more than two physical drives are configured in RAID-0. IOW are all four drives mirrors of each other? Most AppleRAID RAID-0 examples show using two same-size drives, and there is no further info given about how different sizes or more than two drives in the RAID-1 set would be configured.

    I strongly recommend using SoftRAID or SoftRAID Lite for this, not AppleRAID. It avoids using the terminal commands and also is higher performance. In my limited testing on several two-drive Thunderbolt RAID-0 arrays, benchmarks were about 15% faster using SoftRAID vs AppleRAID:

    The other problem with AppleRAID after El Capitan is there’s no GUI method to check the disk subsystem if you have an abrupt shutdown. You may only created a new RAID volume infrequently but uncontrolled shutdowns are more frequent, especially if you have a bunch of machines. Apple removed that from the GUI, so the only way is doing it from terminal. I also don’t think AppleRAID has any kind of “callback” notification of a drive failure. With RAID-1 you could have a failure (or several) and never know it until the last one fails. SoftRAID provides this.

    Also SoftRAID has excellent customer support and is very fast to fix things. My only relationship is as a user who long used AppleRAID and got tired of issuing terminal commands due to El Capitan lobotomizing Disk Utility.

  • Ted Irving

    July 29, 2016 at 11:51 pm

    Ah Nice! Great info. Appreciate it. Will head to SoftRaid.

    Ted Irving
    ENG Cinematographer

  • John Rofrano

    July 30, 2016 at 3:01 am


    You might want to read up on the different RAID strategies even if you don’t use AppleRAID.

    The command you issued did exactly what you told it to do. You asked for a RAID 1 mirror across 4 drives and that’s what it created. When you have drives of different sizes, the usable capacity of each drive in the the RAID will default to the size of smallest drive. So a 3TB + 2TB drive can never be more than a 2TB + 2TB drive because every drive must be the same size and since you can’t format a 2TB for 3TB but you can format a 3TB drive for 2TB, that’s what happens. So that command made a mirror (meaning every drive has the exact same data) with 4 x 2TB drives which yields 2TB of capacity copied 4 times (mirrored)!

    Now I realize that’s not what you wanted. From the sound of your description, I believe that what you wanted was a RAID 0 which adds the drive capacities together but even then, it can only add drives of the same size so your 3TB drive gets treated like a 2TB drive and you would get an 8TB array (2TB+2TB+2TB+2TB) in a RAID 0 stripe. The command for that is:

    diskutil appleRAID create stripe Backup JHFS+ disk5s2 disk6s2 disk7s2 disk8s2

    Personally I would never make a RAID 0 with 4 disks because it one fails you loose the whole thing. With 4 disks you really want a RAID 5 but you will lose the capacity of one disk for parity so that the array can be rebuilt if a drive fails. That would make a 6TB RAID 5 from 4 x 2TB disks.

    So even if you buy SoftRaid, I would be very careful to understand the implications of creating a 4 disk RAID 0. It will be crazy fast, but if one drive fails… all will be lost!


  • Ted Irving

    July 30, 2016 at 10:21 pm

    Appreciate the info. Yeah kinda new for me. I was following some directions from a friend and really but in the wrong code. I went back and deleted the mirror and went back for the stripe set, or JBOD. I know it’s not the best but I’ll play around with RAID 0, 1, and maybe 5. I’ve been using a SansDigital external SATA case with four drives and HiPoint RAID management software. I recently bought a new Sonnettech USB3/Sata PCIe card so my Highpoint web RAID gui doesn’t work anymore. That led me to the Apple Terminal code. But I believe I’ll go after the SoftRaid. I’ll make a decision here this weekend but appreciate all the info. I basically use the mass storage as a TimeMachine backup of all my work from the three internal SATA drives I have. All of which are 2TB drives. And by Christmas I’ll bump up the system drive to an SSD, then update the internals to SSD. As soon as they get bigger. LOL

    Will do the homework! Thanks again.

    Ted Irving
    ENG Cinematographer

  • John Rofrano

    July 31, 2016 at 4:21 am

    [Ted Irving] “And by Christmas I’ll bump up the system drive to an SSD”

    It’s important to note that the 2010 Mac Pro only supports Serial ATA 3Gb/s (SATA2) hard drives and almost all new SSDs are Serial ATA 6Gb/s (SATA3) so they will only give you 1/2 the throughput that they are capable of if you plug them into the existing internal Serial ATA bus.

    If you really want to increase performance in your 2010 Mac Pro, do what I did and get an OWC Mercury Accelsior E2 PCI Express SSD. These plug into am open PCIe slot, run at Serial ATA 6Gb/s speeds and are actually two SSD’s in a RAID 0 so they are scary fast and work as a boot drive leaving all 4 bays free for other drives. As an added bonus, the card has two external eSATA ports that also support SATA3 speeds. So you can buy external eSATA enclosures now too.

    Here is my Disk Speed Test results for my Mercury Accelsior E2 boot SSD in my 2010 Mac Pro 12-Core:

    These gave the old machine a new life. It boots from the chime to the desktop logon screen in 21 seconds! 😀


  • Ted Irving

    July 31, 2016 at 7:58 pm

    WOW! ok good info. Will look to save and get to that point. By the way, I used the terminal for a new external RAID on my second computer at my other office. Did the simple JBOD setup. However, there is a 4TB, and three 2TB drives in the enclosure. Even with the basic stripe in Terminal the final drive comes out to 8TB total. So, what happened to the other 2TB? Is this a drive order issue?

    Ted Irving
    ENG Cinematographer

  • Jeff Kirkland

    August 1, 2016 at 1:04 am

    Im a little rusty with RAID, but I believe JBOD still has the same limitation. All drives need to be the same size. So your 4tb drive is treated as a 2tb drive so it matches the other three, so your maximum storage is 8tb.


    (For some reason I can\’t edit my own posts so apologies in advance for the stupid mistakes and bad English that I can\’t go back and fix)

    Jeff Kirkland | Video Producer & Cinematographer
    Melbourne, Australia | Twitter: @jeffkirkland

  • John Rofrano

    August 1, 2016 at 1:32 pm

    I thought that JBOD was just concatenating disks so different sizes were allowed. It’s odd that you didn’t see all of the space in a JBOD setup.

    It’s important to point out that you don’t really loose any space. If you make a RAID 0 across 4TB+2TB+2TB you will have a RAID 0 equivalent to 2TB+2TB+2TB (6TB) because the RAID 0 could only use 2TB of the 4TB disk BUT you will still have a free 2TB partition from the unused portion of the 4TB drive that you can format as another disk partition.

    Said another way: RAID does not have to use the entire disk! You can make a 3TB RAID 0 by using 1TB each of 3 larger disks.

    BTW, if you just want one big disk, JBOD is safer because if one disk fails in a JBOD array you only loose that one disks data unlike RAID 0 in which you would loose all of the disks data.


  • Craig Alan

    March 7, 2018 at 12:31 am

    What’s the difference between formatting as JBOD and individually formatting each drive. Is it as simple as you can format them all at once. Is there any advantage to using softraid to format them as JBOD vs individually in disc utility? I would still use SoftRaid to monitor the drives health.
    Will FCP X be much slower with a single drive if kept to no more than 80% full vs a 4 drive raid?

    I just had the raid develop errors that could only be resolved by reformatting the drives and am debating to go with individual drives vs four folders in the raid (I back up to individual drives on a dock using CCC).

    Back up drives and raid drives are 6TB each.

    Imacs (i7); Canon 5D Mark III/70D, Panasonic HPX250P, FCP X 10.3, teach video production in L.A.

  • John Rofrano

    March 7, 2018 at 12:53 pm

    [Craig Alan] “What’s the difference between formatting as JBOD and individually formatting each drive.”

    For a hardware RAID there is no difference. Placing a hardware RAID in JBOD mode turns off the RAID controller for those disks so that you can manage the disks independently. I don’t know if it means the same thing to SoftRAID as I’ve never used SoftRAID.

    [Craig Alan] ” Is it as simple as you can format them all at once.”

    Not with a hardware RAID. They will still present themselves as individual disks to be formatted separately. You can make them look like one big Logical Volume by spanning them. I don’t know if SoftRAID acts as a Local Volume Manager in JBOD mode. You would have to ask SoftRAID support. If it does, they do look like one big disk because an LVM takes several Physical Volumes and makes the one Logical Volume to the OS but I’m not sure what the recovery procedure is if one disk fails. It would be better in my view to just mount them as individual disks so that if one fails you only loose that one volume unless SoftRAID says that their JBOD mode does the same.

    [Craig Alan] “Is there any advantage to using softraid to format them as JBOD vs individually in disc utility? I would still use SoftRaid to monitor the drives health.”

    Unfortunately I’m not familiar with SoftRAID. I have an AppleRAID controller in my Mac Pro which is a hardware RAID. JBOD stands for “Just a Bunch Of Disks”. It is a way to turn off the RAID controller on a set of disks so that you can manage them separately. I would imagine that JBOD in SoftRAID would be the same thing but I’m not sure since I’ve never used that software (sorry).

    [Craig Alan] “Will FCP X be much slower with a single drive if kept to no more than 80% full vs a 4 drive raid?”

    It will be slower. Whether you can feel it or not depends on how big the files are that you are editing. If they are small enough for a single drive to handle then using a 4 drive RAID won’t provide any noticeable speed benefit because disk I/O is not your bottleneck. If, however, you are editing files large enough to have a multi-disk RAID be beneficial, then using only one disk will be slower.


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