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I did search a lot and found nothing on this exact matter. I have a Synology DS2018J NAS with 2 disks 4GB each and EXT4 file system on both. I want to change the file system on both to BTRFS, and I have in mind this:

  • deactive one disk
  • format it with BTRFS
  • reactivate it
  • wait until it synchs the contents with the other disk
  • do the same with the other disk

I know that this could be wrong or there can be even more steps (don't know), but I'm not expert on this and found nothing on the matter, so that's why I'm asking.

Thanks!

Fer B.
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1 Answers1

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No. RAID, including SHR, doesn't synchronize files¹ – it synchronizes disk blocks. The entirety of the disk is therefore subject to RAID mirroring – not just file contents and metadata but the filesystem structures as well (as those are just "data" as far as the disk knows); the resync process will just discard whatever upfront formatting you've done and will copy the existing Ext4 structures onto the new disk.

¹ Some filesystems do have file-level "RAID" – e.g. Btrfs does, though I believe Synology does not use that feature – but because this feature is part of the filesystem, it also inherently requires both disks to have the same filesystem. (And not merely the same filesystem type – with Btrfs "raid" you wouldn't have two Btrfs filesystems, you would literally have the same filesystem spanning both disks.)

u1686_grawity
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