Can't Install Yosemite on RAID0 Array

Discussion in 'OS X Yosemite (10.10)' started by jimmyco2008, Aug 2, 2014.

  1. jimmyco2008 macrumors regular

    Joined:
    Jan 8, 2014
    #1
    Hey all,

    I have a Mac Mini with two SSDs in RAID0 (try not to grill me on how against that you might be), and I'm unable to install Yosemite because AppleRAID isn't supported or something to that effect.

    Yet, I've read in other threads that people have Yosemite on their RAID0 arrays...

    The SSDs are Intel 240(GB)'s (not Apple-official). Currently, I have Mountain Lion installed, but that was only after trying my Yosemite PB1 USB installer when the array was fresh and lacked any OS. I've also tried the DP installer .app and the PB1 .app when launched on the array locally. When launched in Mountain Lion, the installer simply force closes. Might be a ML thing, I'll upgrade to Mavericks while passing the time, but I'm not holding my breath.
     
  2. stix666 macrumors regular

    Joined:
    Nov 13, 2005
    #2
    I installed Yosemite on a hdd, then cloned that to my raid0 using carbon copy cloner. Works perfectly.
     
  3. jimmyco2008 thread starter macrumors regular

    Joined:
    Jan 8, 2014
    #3
    Thanks for the reply.

    To be clear, you did so because you encountered the same error I did?
     
  4. haravikk macrumors 65816

    Joined:
    May 1, 2005
    #4
    I think the main problem you'll have with AppleRAID is that the installer can't create a Recovery HD on it. The way I got around it before was to leave the disks as two separate volumes and install OS X onto one of them (to create the Recovery HD), then I started up another OS X installation (on a USB stick, the Recovery HD might actually be okay for this now), partitioned the second drive to match the first, then created a new AppleRAID with the two large partitions.

    I also converted it to a Core Storage volume for good measure, as this then allowed me to enable FileVault later, once the volume was created I then installed OS X normally onto it.


    The initial installation to one disk is straightforward. Once you're done with that you need to restart to another bootable system (again, Recovery HD might actually be okay for this), at which point you can use Disk Utility to partition to the second disk to match the first; you don't strictly need to do this, but I did so I had space for a second Recovery HD (so I would still have one regardless of which disk fails). You can then convert the two largest partitions into an AppleRAID, and create a Core Storage volume.

    For this last step you'll probably need to use the Terminal (as I don't believe the convert command works for AppleRAID volumes), first run "diskutil list" and figure out the device number (/dev/diskX) of your RAID volume, then run the command "diskutil cs create 'NAME' DEV" replacing NAME with any desired name and swapping DEV for the device number you got. Once that's done you'll be given an ID number for the newly created logical volume group that looks like 32BBCA9C-511D-47BA-9F29-D2F6BA02CEAF. Now you can run "diskutil cs createVolume ID jhfs+ 'NAME' 100%" replacing ID for the ID you got from the last step (if you didn't see it then run "diskutil cs list" and find the ID for the logical volume group with your RAID in it) and swap NAME for the name of the new volume (you can change this in the usual ways for a volume).

    If the Core Storage stuff is a bit too daunting, and you don't care about FileVault then you should be able to just ignore that, but personally I'm still hoping Apple have more Core Storage features to come, so it's probably a good idea to do it.

    But yeah, I'm pretty sure the problem is actually the inability of the installer to create the Recovery HD, rather than an issue with the AppleRAID, i.e - the error is actually about trying to create a Recovery HD on an AppleRAID, rather than the actual installation failing. Once you've got a Recovery HD you shouldn't get this error anymore.
     
  5. stix666 macrumors regular

    Joined:
    Nov 13, 2005
    #5
    Yes. Not an issue, as this is a mac pro with loads of bootable partitions and backups.
     
  6. jimmyco2008 thread starter macrumors regular

    Joined:
    Jan 8, 2014
    #6
    Thank you haravikk!

    I've since decided that RAID0ing two SSDs is kind of fruitless (I was getting nary 1GB/s read speeds though!), especially since I won't be transferring a lot of exceptionally-large files.

    This is very useful information, though, and I'll definitely use it should I opt for RAID again in the future, not to mention I'm sure it'll help many people, you and I aren't the only ones who explore RAID with OS X Yosemite.
     
  7. AnilPani, Nov 30, 2014
    Last edited: Nov 30, 2014

    AnilPani macrumors newbie

    Joined:
    Jul 31, 2010
    #7
    Hi haravikk,

    Thank you for your informative posts!

    I am planning on installing two apple SSDs in a Mac mini and am trying to decide what the best configuration would be. I definitely want to have them function as a single volume. The question is whether to combine them in a RAID 0 array or to simply join them in a Core Storage volume. Potential issues with TRIM support, Boot, and Recovery partitions using a RAID 0 array make me a little nervous, but maybe the performance gain is worth it?

    In your experience, is there a way to get the best of both worlds (as the above post would suggest)? If so, do you have a tutorial I could follow? I am reasonably tech savvy, but am not adept at terminal/unix commands.

    Thanks in advance for your help!

    -Pani
     
  8. haravikk macrumors 65816

    Joined:
    May 1, 2005
    #8
    If by best of both you mean between RAID and Core Storage then there may be some confusion as to what you want Core Storage for.

    The main reason you would want to combine two disks into one with Core Storage, is if one is an SSD and one is an HDD, as this will create a Fusion Drive (where common data is moved to the SSD to give you a speed boost), but this won't do anything for you if both disks are SSDs, actually it will most likely just increase wear on one of the drives. If this isn't the case then joining two drives is concatenation, in which case data is written to one disk until it fills, then spills over onto the second, third and so-on. This gives you plenty of capacity, but has no speed benefits, while giving you the same vulnerability to disk failure as a RAID-0 (if one disk fails, you lose the set); while technically it's easier to recover data on a concatenated set, it's not something you want to rely on.

    So when it comes to combining disks then RAID is really what you want. RAID-0 to split data evenly between the disks, resulting in level wear, double the capacity and potentially double speed for large files (smaller files won't see much benefit), but at the risk of data loss if one drive files. Or you can do a RAID-1, which copies data onto both disks so a disk failure won't lose anything but you won't increase capacity. In theory you should also improve performance as there are still two drives to load data from, but I've never seriously used RAID-1 with AppleRAID, so I don't know if it gives any acceleration.

    However, once you've created your AppleRAID you can still convert it to a Core Storage volume, which will allow you to encrypt it (or possibly more if Apple ever adds more features). I only really mentioned it though because some of the Core Storage tools don't work with AppleRAID, in particular I was never able to convert an existing AppleRAID with a file system on it to Core Storage like you can with a single disk, but you can create a new Core Storage volume from an AppleRAID (wiping it in the process) just fine, so it's worth considering at the start for this reason.

    Since both RAID types expect identical members (disks or partitions) you need to consider where your Recovery HD will go. If you're fine just creating an OS X installer USB stick then you can do that and forget about it, but if you want an internal one then what you can do is actually put one on each drive in the array (so if one fails, you still have a Recovery HD). The basic steps to do this would be:

    • First of all you'll want to create an install disk on a USB stick, external drive etc.
    • Install OS X normally one of your drive (let's call it A). This will create a Recovery HD and a main system partition.
    • You want to clone the structure of A onto the other drive (call it B), either by creating the same partition structure or just cloning the whole drive, the latter is easier but will copy stuff you don't need.
    • Booting up from the installer disk you created, you'll now take the largest partitions of A and B and combine them into a RAID-0 or RAID-1, depending upon your choice of performance + capacity vs redundancy.
    • Once this done you convert the new AppleRAID device to a Core Storage volume (though you'll probably need to use the command line to do this).

    I know these steps aren't very specific, I can try to find more specific commands, but I don't have spare volumes lying around so I can't completely confirm they would work.
     
  9. AnilPani macrumors newbie

    Joined:
    Jul 31, 2010
    #9
    Thanks for the info! My plans have changed a little. I will still have 2 SSDs, but they will be different sizes. That means I will not be able to join them in a RAID 0 array, correct? If not, should I join them in a JBOD array?

    Finally, are there any advantages of creating a CoreStorage Volume from an Apple RAID from besides File encryption?

    Thanks again for all of the help and advice!
    -Pani
     
  10. haravikk macrumors 65816

    Joined:
    May 1, 2005
    #10
    Actually no, but the RAID-0 won't take advantage of any excess space on the larger drive. For example, if you have one 256gb drive, and one 512gb drive, you'll end up with a 2x 256gb RAID-0, the extra 256gb is wasted.

    However, you could partition the larger of the two drives, in this example you'd use all of the 256gb drive, and split the larger one into two separate partitions, and create the RAID-0 from the small drive, plus one partition on the big drive, as long as they're the same size this will work.

    The problem though is what to do with the leftover partition, as it isn't advisable to do anything demanding on it, as it'll slow down the RAID.



    One other thing to consider is whether one SSD is much faster than the other; as you could still create a Fusion Drive. You just use both drives to create a Core Storage volume, and it should detect that one is faster and use it as the fast disk in the Fusion Drive. If the faster drive is also the bigger of the two though then you probably won't see much benefit.

    Currently no, though my personal preference is still to do it just in case any new core storage feature comes along, or I later decide to encrypt the volume, as enabling them will be much easier if the volume is already a Core Storage one, since the conversion process doesn't seem to work for an AppleRAID.

    You can also actually create a Fusion Drive from a RAID array, but not with only two disks.
     
  11. Homer69 macrumors newbie

    Homer69

    Joined:
    Jul 30, 2015
    #11

    My question is, how do I install Clover to an existing RAID0 volume.
    I have no problem booting this RAID volume from a USB, but run into a road block trying to incorporate Clover to boot directly without the help of the USB drive. I tried just about most suggestions elsewhere yet the machine won't recognize any bootable volume.
    Thank you
     

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