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Improve detail regarding distribution of RAID-stripes on "btrfs device usage" output (btrfs-progs 4.4)

DISCUSSION Christian Rohmann 1 participant 1 message Jan 19, 2016 Btrfs file system

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Christian Rohmann

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Hello all,

I am currently running a balance on a RAID6 with former 8 devices (4TB each) to which I added 4 more (1TB each) and it now has a total 12. The balancing is still running but looking at "btrfs device usage" already gives some hint on the gradually changing data distribution of the RAID6:

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btrfs device usage $btrfsfilesystem

/dev/sdb, ID: 1
Device size: 3.64TiB
Data,RAID6: 3.37TiB
Data,RAID6: 101.92GiB
Metadata,single: 8.00MiB
Metadata,RAID6: 6.34GiB
Metadata,RAID6: 448.00MiB
System,single: 4.00MiB
System,RAID6: 2.00MiB
Unallocated: 161.78GiB

/dev/sdc, ID: 2
Device size: 3.64TiB
Data,RAID6: 3.37TiB
Data,RAID6: 101.92GiB
Metadata,RAID6: 6.34GiB
Metadata,RAID6: 448.00MiB
System,RAID6: 2.00MiB
Unallocated: 161.79GiB

/dev/sdd, ID: 3
Device size: 3.64TiB
Data,RAID6: 3.37TiB
Data,RAID6: 101.92GiB
Metadata,RAID6: 6.34GiB
Metadata,RAID6: 448.00MiB
System,RAID6: 2.00MiB
Unallocated: 161.79GiB

/dev/sde, ID: 4
Device size: 3.64TiB
Data,RAID6: 3.37TiB
Data,RAID6: 101.92GiB
Metadata,RAID6: 6.34GiB
Metadata,RAID6: 448.00MiB
System,RAID6: 2.00MiB
Unallocated: 161.79GiB

/dev/sdf, ID: 5
Device size: 3.64TiB
Data,RAID6: 3.37TiB
Data,RAID6: 101.92GiB
Metadata,RAID6: 6.34GiB
Metadata,RAID6: 448.00MiB
System,RAID6: 2.00MiB
Unallocated: 161.79GiB

/dev/sdg, ID: 6
Device size: 3.64TiB
Data,RAID6: 3.37TiB
Data,RAID6: 101.92GiB
Metadata,RAID6: 6.34GiB
Metadata,RAID6: 448.00MiB
System,RAID6: 2.00MiB
Unallocated: 161.79GiB

/dev/sdh, ID: 7
Device size: 3.64TiB
Data,RAID6: 3.37TiB
Data,RAID6: 101.92GiB
Metadata,RAID6: 6.34GiB
Metadata,RAID6: 448.00MiB
System,RAID6: 2.00MiB
Unallocated: 161.79GiB

/dev/sdi, ID: 8
Device size: 3.64TiB
Data,RAID6: 3.37TiB
Data,RAID6: 101.92GiB
Metadata,RAID6: 6.34GiB
Metadata,RAID6: 448.00MiB
System,RAID6: 2.00MiB
Unallocated: 161.79GiB

/dev/sdj, ID: 9

   Device size:           931.00GiB
   Data,RAID6:            101.92GiB
   Metadata,RAID6:        448.00MiB
   Unallocated:           828.64GiB

/dev/sdk, ID: 10

   Device size:           931.00GiB
   Data,RAID6:            101.92GiB
   Metadata,RAID6:        448.00MiB
   Unallocated:           828.64GiB

/dev/sdl, ID: 11

   Device size:           931.00GiB
   Data,RAID6:            101.92GiB
   Metadata,RAID6:        448.00MiB
   Unallocated:           828.64GiB

/dev/sdm, ID: 12

   Device size:           931.00GiB
   Data,RAID6:            101.92GiB
   Metadata,RAID6:        448.00MiB
   Unallocated:           828.64GiB

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The old disks now show two lines with RAID6 data. Likely it's the old, 8-device stripes vs. the new 12-device stripes. But there seems to be no detail available to show what the difference of those two lines might be. Maybe adding the number of stripes next to the data storage style could help i.e.

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/dev/sdi, ID: 8
Device size: 3.64TiB
Data,RAID6,8-way-striped: 3.37TiB
Data,RAID6,12-way-striped: 101.92GiB
Metadata,RAID6,8-way-striped: 6.34GiB
Metadata,RAID6,12-way-striped: 448.00MiB
System,RAID6: 2.00MiB
Unallocated: 161.79GiB
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Regards

Christian