4 Replies Latest reply: Aug 24, 2012 12:09 PM by Mr. Latte
Mr. Latte Level 1 Level 1 (0 points)

Hi, I have mirrored build of two identical 1TB HDD in my Xserve Late 2006 (RAID 1) in Bay 2 and Bay3. When I took one HDD out and connected it as an external drive to my MacBook Pro, only the first partition appeared. That is, for instance, I have RAID partition A1, A2, A3 in Xserve but only A1 appears when the drive is connected to MacBook Pro as an external drive. Is there any way to let partition A2, A3 appear too? Thanks.


Mac OS X (10.7.3), iMac, MacBook Pro, Mac Pro, iPhone, iPad, and more
  • 1. Re: RAID1 Partitions disappeared when one of the mirrored HDD is used as an external drive for data rescue.
    Camelot Level 8 Level 8 (45,790 points)

    What do you see when you launch Disk Utility on the MacBook Pro?

     

    Do you see all three partitions? or only one?

    Can you select the additional partitions and mount them manually?

  • 2. Re: RAID1 Partitions disappeared when one of the mirrored HDD is used as an external drive for data rescue.
    Mr. Latte Level 1 Level 1 (0 points)

    Hi, Camelot,

     

    In Disk Utility of my MBP, just partition A1 appeared, my A2, A3 partitions are gone for both working RAID1 drivers. There are no A2, A3 partitions showing up and hence I could not mount them. And the RAID1 drivers are perfectly fine. They just don't show up on my iMacs nor Minis. About a year ago, I had the same problem but I did not pay too much attention to it because when the RAID1 HDDs go with Apple ADM into the RAID Card interconnect Backplane Board, they have no problem of showing all RAID paritions.

     

    So this means to show all RAID1 partitions, I must have a working RAID Card and a working Xserve.

     

    Apparently, this poses a danger to anyone who is using RAID1 with the Apple RAID Card out there. If their RAID Card goes down, or if their Xserve goes down, this means they have no way of getting out the data stored in other partitions despite the fact that they have both working RAID1 drivers.

     

    So you may ask why not just use a single partition for my RAID1 design. The reason is that I prefer to partition HDD because it is good for HDD lifespan. I don't like to design my parition schema to be just a single big parition with 1T Hard Drive since all data are going to be stored scattered and hence, taking longer for spindle reading.

  • 3. Re: RAID1 Partitions disappeared when one of the mirrored HDD is used as an external drive for data rescue.
    Camelot Level 8 Level 8 (45,790 points)

    Oh, I didn't realise you were using the hardware RAID card for this. In that case, yes, that makes sense, you won't see the other partitions because they're handled by the RAID card. I admit I'd never tried it with a RAID 1 mirror where you might expect to - I've only used RAID 5 on the hardware cards where there's no expectation, of course, to pull a drive to relocate the data.

    So you may ask why not just use a single partition for my RAID1 design. The reason is that I prefer to partition HDD because it is good for HDD lifespan. I don't like to design my parition schema to be just a single big parition with 1T Hard Drive since all data are going to be stored scattered and hence, taking longer for spindle reading.

    I don't agree with most of this statement. I've not seen anything that indicates partitioning improves lifespan - for any given data, the disk spins the exact same number of times, and the heads move the same number of times, regardless of the partitioning - partitioning is only a logical, not a physical, construct.

    As for the data being scattered and spindle latency, that's nowhere near the problem it used to be in the past thanks to faster spindles and larger caches. In addition, Mac OS X uses a dynamic reallocation/fragmentation system that automatically (re)allocates files as they're used, meaning you don't have the level of fragmentation that you used to have.

    The primary benefit of partitioning is to restrict file system sizes so that you don't get a runaway proceess filling up the entire disk. Even that is less of a problem - when an 8GB drive was large it didn't take much to fill it, but you'd have to have a pretty rampant process to fill up a 1TB drive before alarms started ringing.

  • 4. Re: RAID1 Partitions disappeared when one of the mirrored HDD is used as an external drive for data rescue.
    Mr. Latte Level 1 Level 1 (0 points)

    Okay, that explains it.

     

    This leaves me no option but to use a single partition when using hardware RAID1.

     

    I've got some questions:

    Do you know if I would have the partition missing if I opt to use hardware RAID5?

     

    If I use software RAID1/RAID5, would the partition be missing too? I've heard that SoftRAID is the popular one on the street now. Like you said, I have to have one partition limited for others to upload files for security reasons. Is there any workaround to this partition issue?