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Is it possible to add more than 2 disks for parity in mdadm raid 6? I need to build a storage of 20 disks. How to build a raid that would be reliable?

PetroIvanov
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As far as I could quickly glance, with RAID 6 Linux mdadm does not actually use dedicated parity disks, but rather distributes the parity blocks over the devices that make up the RAID6 array. The number of parity blocks is always 2.

Raid 6

The mathematics allows the calculation of an arbitrary number of parity blocks, but linux raid only uses two, which we call P and Q. As with raid-5, the parity blocks are scattered amongst the devices
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Raid 6 is the only raid level where mdadm may complain that it cannot carry out a conversion directly between levels 4, 5 and 6. This is down to the way the parity blocks are scattered amongst the devices.

(Source: https://raid.wiki.kernel.org/index.php/A_guide_to_mdadm - emphasis mine)

HBruijn
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DO NOT create a R6 with 20 disks - that's what R60 is for - just do that, and HBrujin is correct - inherently R6 stripes the protection data around all disks.

Chopper3
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