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If I convert a disk from basic to dynamic is it possible to format it to master boot record (MBR) or is it just possible to format with GPT?

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1 Answer 1

There are two entirely orthogonal dimensions here:

  • Partition table type -- This is MBR vs. GPT. The disk may be one or the other, but not both. (Hybrid MBRs are, in a sense, both, but they're illegal by the GPT spec.)
  • Basic vs. dynamic disks -- In Microsoft terminology, a "basic disk" is an MBR or GPT disk on which filesystems reside directly in partitions. A "dynamic disk," OTOH, uses Microsoft's Logical Disk Manager (LDM) to enable creating filesystems that consume part of a partition or that span multiple partitions. This is Microsoft's version of a logical volume management (LVM) configuration. By whatever name, dynamic/LDM/LVM configurations are much more flexible -- but also more complex -- than "basic" disk setups.

Thus, the MBR or GPT configuration of a disk exists "underneath" its configuration as "basic" vs. "dynamic." In setting up a disk, you normally select MBR vs. GPT and then select "basic" vs. "dynamic" -- although in practice, an OS installer may make both these decisions for you, and may not even tell you what decisions it's making.

Unfortunately, the Windows partitioning software has a tendency to convert "basic" disks to an LDM/dynamic configuration without warning. This can wreak havoc if you're multi-booting or sharing a removable disk with another OS. If you run into this problem, you can use tools like EaseUS Partition Master to convert back to a "basic" (plain MBR or GPT) setup.

Most tools can convert MBR to GPT or vice-versa only by completely deleting all the partitions on the disk. IIRC, EaseUS can do so losslessly. So can my GPT fdisk (gdisk) software, albeit with some caveats concerning partition size and layout.

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