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16TB limit with EXT4

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  • 16TB limit with EXT4

    I've been using VB since its beginning. I have 3 (online, backup, spare) with a massive music and movie collection; hence a large amount of storage (>12TB). I was doing a rebuild of 1 over the weekend and I noted that the volume size limit under EXT4 is 16TB. I was planning on 24TB in this new machine, that would give me a few years without the need to expand. I found out (eventually !!) that EXT4 has a volume limit of 16TB. I know for most people that's not an issue (yet !) but clearly looking to the future VB will need to go beyond 16TB. I learned that the new brfs filing system has considerably higher volume limits. Do you think it would be practicable to upgrade an EXT4 (VB25) machine to a btfs file system?

  • #2
    Sean, how did you find the ext4 limit ? Did you try to combine three 8TB drives using vgcreate and lvcreate?

    A quick google brought up this - https://docs.fedoraproject.org/en-US...lesystems.html which indicates 50TB limit.

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    • #3
      Originally posted by Wirrunna View Post
      Sean, how did you find the ext4 limit ? Did you try to combine three 8TB drives using vgcreate and lvcreate?

      A quick google brought up this - https://docs.fedoraproject.org/en-US...lesystems.html which indicates 50TB limit.
      I got to the last step in the 2nd drive install sequence WiKi ( 'resize2fs /dev/StorageVM/lv_storage ' ) and received the error message basically saying 'volume too big for 32 bit addressing'. I then researched EXT4 and found out that its limited to 16TB (file size). I assumed from that that a LVM cannot be larger than 16TB, perhaps I'm wrong but In the end I just used the primary drive at 12TB and added in one at 4TB. That all worked fine.
      Last edited by SeanMiddleton; 01-21-2020, 05:31 AM.

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      • #4
        Originally posted by SeanMiddleton View Post

        I got to the last step in the 2nd drive install sequence WiKi ( 'resize2fs /dev/StorageVM/lv_storage ' ) and received the error message basically saying 'volume too big for 32 bit addressing'. I then researched EXT4 and found out that its limited to 16TB (file size). I assumed from that that a LVM cannot be larger than 16TB, perhaps I'm wrong but In the end I just used the primary drive at 12TB and added in one at 4TB. That all worked fine.
        I suspect that if you wiped the MBR & partition table of the disks and then started again with 64bit Linux you could get your 24TB.
        If one of the disks was set up with 32bit linux then that probably limits all subsequent operations involving that disk to 32bit restrictions.

        To format (remove) your MBR & partition table - virtually a "factory restore" but quick as only the front of the disk is clobbered

        dd if=/dev/zero of=/dev/sdX bs=512 count=1

        ... where /dev/sdX is the drive you want to remove the MBR & partition table from.

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        • #5
          Originally posted by Wirrunna View Post

          I suspect that if you wiped the MBR & partition table of the disks and then started again with 64bit Linux you could get your 24TB.
          If one of the disks was set up with 32bit linux then that probably limits all subsequent operations involving that disk to 32bit restrictions.

          To format (remove) your MBR & partition table - virtually a "factory restore" but quick as only the front of the disk is clobbered

          dd if=/dev/zero of=/dev/sdX bs=512 count=1

          ... where /dev/sdX is the drive you want to remove the MBR & partition table from.
          Interesting idea. Both of the 12TB drives I initially tried were brand new and hadn't previously been played with. Given that, I'm not sure they were locked into a 32 bit environment. But, perhaps earlier commands in the 'install second drive' WiKi had locked them in a 32 bit environment ???Is VB2.4 32 bit ??

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          • #6
            Sean, further digging confirms your findings of 16TB maximum file size - https://access.redhat.com/solutions/1532 and https://access.redhat.com/articles/rhel-limits .

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