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I've combined 8 16tb drives in raid 6. In my theory the array should report its size 96.00tb, but instead mdadm reports the total array size 87.32tb, not 96tb. Also, It says I have 14.55tb of used dev size.
$ sudo mdadm --detail /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Fri Nov 25 14:53:10 2022
Raid Level : raid6
Array Size : 93754475520 (87.32 TiB 96.00 TB)
Used Dev Size : 15625745920 (14.55 TiB 16.00 TB)
Raid Devices : 8
Total Devices : 8
Persistence : Superblock is persistent
Intent Bitmap : Internal
Update Time : Sun Nov 27 11:57:05 2022
State : clean
Active Devices : 8
Working Devices : 8
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 512K
Consistency Policy : bitmap
Name : XXXXXXX
UUID : 8f8eaee0:2b760d64:1fec58e7:ae9f0b0b
Events : 27584
Number Major Minor RaidDevice State
0 8 1 0 active sync /dev/sda1
1 8 17 1 active sync /dev/sdb1
2 8 33 2 active sync /dev/sdc1
3 8 49 3 active sync /dev/sdd1
4 8 65 4 active sync /dev/sde1
5 8 81 5 active sync /dev/sdf1
6 8 97 6 active sync /dev/sdg1
7 8 113 7 active sync /dev/sdh1
fdisk shows the same sectors for each partition on the disk.
$ for i in a b c d e f g h; do sudo fdisk "/dev/sd$i" -l ;done
Disk /dev/sda: 14.55 TiB, 16000900661248 bytes, 31251759104 sectors
Disk model: MG08SCA16TE
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 3CAD746E-3B91-1F46-8BF2-0FA467D9EA4E
Device Start End Sectors Size Type
/dev/sda1 2048 31251759070 31251757023 14.6T Linux RAID
Disk /dev/sdb: 14.55 TiB, 16000900661248 bytes, 31251759104 sectors
Disk model: MG08SCA16TE
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 23797260-8081-4541-A645-574EB9660ED6
Device Start End Sectors Size Type
/dev/sdb1 2048 31251759070 31251757023 14.6T Linux RAID
Disk /dev/sdc: 14.55 TiB, 16000900661248 bytes, 31251759104 sectors
Disk model: MG08SCA16TE
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 89A823DE-0662-9D49-B100-440508C4C05F
Device Start End Sectors Size Type
/dev/sdc1 2048 31251759070 31251757023 14.6T Linux RAID
Disk /dev/sdd: 14.55 TiB, 16000900661248 bytes, 31251759104 sectors
Disk model: ST16000NE000-2RW
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 37365809-1E64-F748-B4B4-6BD675969198
Device Start End Sectors Size Type
/dev/sdd1 2048 31251759070 31251757023 14.6T Linux RAID
Disk /dev/sde: 14.55 TiB, 16000900661248 bytes, 31251759104 sectors
Disk model: MG08SCA16TE
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 453FE0BD-047A-BC4E-9221-E21DAD8FAE10
Device Start End Sectors Size Type
/dev/sde1 2048 31251759070 31251757023 14.6T Linux RAID
Disk /dev/sdf: 14.55 TiB, 16000900661248 bytes, 31251759104 sectors
Disk model: ST16000NE000-2RW
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 81416E80-49BC-6949-9122-4ECD6BDA6604
Device Start End Sectors Size Type
/dev/sdf1 2048 31251759070 31251757023 14.6T Linux RAID
Disk /dev/sdg: 14.55 TiB, 16000900661248 bytes, 31251759104 sectors
Disk model: WUH721816ALE6L4
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 511C012C-EA45-D042-8825-49D7FEF57277
Device Start End Sectors Size Type
/dev/sdg1 2048 31251759070 31251757023 14.6T Linux RAID
Disk /dev/sdh: 14.55 TiB, 16000900661248 bytes, 31251759104 sectors
Disk model: WUH721816ALE6L4
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: E3D62C63-87CB-CF4D-B8E5-BC69B3672D25
Device Start End Sectors Size Type
/dev/sdh1 2048 31251759070 31251757023 14.6T Linux RAID
Here is my /proc/mdstat.
$ cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4] [linear] [multipath] [raid0] [raid1] [raid10]
md0 : active raid6 sdh1[7] sdg1[6] sdf1[5] sde1[4] sdd1[3] sdc1[2] sdb1[1] sda1[0]
93754475520 blocks super 1.2 level 6, 512k chunk, algorithm 2 [8/8] [UUUUUUUU]
bitmap: 0/117 pages [0KB], 65536KB chunk
unused devices: <none>
Last edited by seolha314 (2022-11-27 13:31:53)
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In my theory the array should report its size 96.00tb
Perhaps you should show your work?
How did you come to that conclusion?
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In my theory the array should report its size 96.00tb
Perhaps you should show your work?
How did you come to that conclusion?
8 times 16tb minus two drives for parity, that returns 96tb, right?
And I have used this command to make an array:
# mdadm --create /dev/md0 --level=6 --raid-devices=8 /dev/sd[a-h]1
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RAID6
*Raw Storage: 128.0 TB / 128000.0 GB
*Usable Storage: 87.3 TB / 89407.0 GB
RAID6 uses two disks for Parity and requires at least four drives to be used.*Usable storage is the actual post-format amount where kilo = 1024, not 1000
https://www.servethehome.com/raid-calculator/
This might help, some light reading...
https://mirrors.edge.kernel.org/pub/lin … /raid6.pdf
Last edited by Zod (2022-11-27 13:20:32)
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Oh, a common mistake with TB and TiB...
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