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Jasmine Lognnes
Asked: 2017-02-22 02:52:15 +0800 CST

Is GPT needed on a 16 TB data disk?

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I have made /dev/sdb which is a 16 TB disk using hardware RAID, where I am temped to put XFS directly on /dev/sdb without making partitions. In the future will I need to expand this to double the size.

The hardware is an HP ProLiant DL380 Gen 9 with 12 SAS disk trays in the front.

One advantage of not making partitions is that a reboot isn't needed, but are things different on >2 TB disks?

Do I need to have a GPT, or can I run into trouble when expanding the RAID array and XFS without one?

linux raid hp xfs gpt

2 Answers

  1. GPT is about partitioning disks and partition tables. So if you plan to put the XFS filesystem on the disk, without having partitions you do not need a GPT label.

    The GPT label would be destroyed as soon as you create the filesystem on /dev/sdb. One thing to remember is that GPT also creates a backup label at the end of the disk. Some tools ( partprobe or partx ) try to "repair" the GPT of a disk if a backup is found. Some tools even do that without asking, which then would result in a thrashed filesystem. Some EFI BIOSes also provide such a "feature".
    So you should ensure that there is no backup GPT label on /dev/sdb by using e.g. gdisk.

    In general I would recommend to partition the disk, which is also helpful for other team members or admins to recognize that the disk is in use. It's e.g. harder to tell if a disk is in use when it is not partitioned.
    You also normally do not need a reboot after partitioning the disk.

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  2. Best Answer

    You can do this without any problems...

    I'm assuming /dev/sdb is a separate HP Smart Array Logical Drive.

    Don't use any partitioning for this setup... Just create the filesystem on the block device:

    mkfs.xfs -f -l size=256m,version=2 -s size=4096 /dev/sdb

    When you want to expand at a later date, add disks and expand the HP logical drive using the hpssacli or Smart Storage Administrator tools.

    You can rescan the device to get the new size with:

    echo 1 > /sys/block/sdb/device/rescan

    Confirm the device size change with dmesg|tail.

    At that point, you can run xfs_growfs /mountpoint (not device name) and the filesystem will grow online!

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