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This is a more theoretical question I ran into after I found out that it is possible with newer Kernels to create partitions on a RAID-volume.

Since Grub2 it is possible to have /boot on a RAID-volume. My basic setup for small servers always looked like this since then:

  • md0 --> ext3/4 --> /swap
  • md1 --> ext3/4 --> /boot
  • md2 --> ext3/4 --> /
  • md3 --> ext3/4 --> /home

Never ran into problems with this. However, it is possible (I don't know since when exactly) to create one RAID-Volume and create multiple partitions on that volume (meaning no LVM but "native" partitions like md0p1 etc.).

So I'm just wondering what's the sense behind this? Are there any performance-related pros to go that way or is this just an organizational "feature"? I seldom experienced Kernel developers to include a feature that doesn't provide an improvement compared to former versions so can anybody explain which environment would profit from such a setup?

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up vote 1 down vote accepted

The ability to create partitions from a volume applies to RAID and any device exposed to the OS like a single SATA/IDE HDD, they are all just block storage volumes to the OS.

2 potential advantages, you essentially move the configuration of your storage from a hardware level to an OS level and you would less reliant on your RAID controller manufacturers tools for configuration and diagnostics/repair.

You will loose flexibility/scalability compared to using multiple raid volumes (such as using a mixed RAID 10 / RAID5 setup, more flexibility with where hot/cold spares are assigned to (so your OS volume may only have minimal spares, but your data volumes multiple spares).

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So am I getting it right that the introduction of this feature was not really a feature orientated action but more of a logical conclusion to treat software-RAID-devices like any other RAID-device or physical device (well besides the pro for minimizing the need for spare volumes)? – Broco Aug 20 '14 at 15:19
@Broco Yes, as far as I know. – NGRhodes Aug 20 '14 at 15:29
Well then you deserve the reputation :D – Broco Aug 20 '14 at 16:46

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