I created a software RAID 5 array one year ago using mdadm v3.2.x (CentOS 6.3) with 3 3TB disks (Seagate ST3000DM001), after few months, I moved/assembled the array to/in Fedora 19 (now Fedora 20). Now, I added tow more disks to it, and grow this array to 4 disks + 1 hot spare. Now, the array size is 8383.55 GiB. Then I created another array (RAID 6) using mdadm v3.3 (Fedora 20) with 5 3TB disks (Toshiba DT01ACA300), but the array size is 8383.18 GiB, which is slightly smaller than 8383.55 GiB. The partition size of each disk in the two arrays are identical (all partitions have 5860531087 logical sectors), so why the array size are different? Is it caused by different mdadm version (I guess so) or different array level or something else? Same question on unix.stackexchange.com: http://unix.stackexchange.com/questions/121310/two-arrays-have-slightly-different-array-size-with-same-size-disks-partitions-w =================== == RAID 5 detail == =================== # mdadm -D /dev/md127 /dev/md127: Version : 1.2 Creation Time : Fri Jan 11 17:56:18 2013 Raid Level : raid5 Array Size : 8790792192 (8383.55 GiB 9001.77 GB) Used Dev Size : 2930264064 (2794.52 GiB 3000.59 GB) Raid Devices : 4 Total Devices : 5 Persistence : Superblock is persistent Update Time : Tue Mar 25 11:04:15 2014 State : clean Active Devices : 4 Working Devices : 5 Failed Devices : 0 Spare Devices : 1 Layout : left-symmetric Chunk Size : 512K Name : RecordBackup01:127 (local to host RecordBackup01) UUID : dfd3bbe7:4b0231fe:9007bc4a:e106acac Events : 7264 Number Major Minor RaidDevice State 0 8 17 0 active sync /dev/sdb1 1 8 33 1 active sync /dev/sdc1 3 8 49 2 active sync /dev/sdd1 5 8 81 3 active sync /dev/sdf1 4 8 65 - spare /dev/sde1 =================== == RAID 6 detail == =================== # mdadm -D /dev/md127 /dev/md127: Version : 1.2 Creation Time : Fri Mar 21 18:12:00 2014 Raid Level : raid6 Array Size : 8790402048 (8383.18 GiB 9001.37 GB) Used Dev Size : 2930134016 (2794.39 GiB 3000.46 GB) Raid Devices : 5 Total Devices : 5 Persistence : Superblock is persistent Intent Bitmap : Internal Update Time : Tue Mar 25 11:18:51 2014 State : active Active Devices : 5 Working Devices : 5 Failed Devices : 0 Spare Devices : 0 Layout : left-symmetric Chunk Size : 512K Name : RecordBackup02:127 (local to host RecordBackup02) UUID : 923c9658:12739258:506fc8b0:f8c5edf3 Events : 8172 Number Major Minor RaidDevice State 0 8 17 0 active sync /dev/sdb1 1 8 33 1 active sync /dev/sdc1 2 8 49 2 active sync /dev/sdd1 3 8 65 3 active sync /dev/sde1 4 8 81 4 active sync /dev/sdf1 =================================== == RAID 5 partitions information == =================================== Model: ATA ST3000DM001-1CH1 (scsi) Disk /dev/sdb: 5860533168s Sector size (logical/physical): 512B/4096B Partition Table: gpt Disk Flags: Number Start End Size File system Name Flags 1 2048s 5860533134s 5860531087s pri Model: ATA ST3000DM001-1CH1 (scsi) Disk /dev/sdc: 5860533168s Sector size (logical/physical): 512B/4096B Partition Table: gpt Disk Flags: Number Start End Size File system Name Flags 1 2048s 5860533134s 5860531087s ext4 primary Model: ATA ST3000DM001-1CH1 (scsi) Disk /dev/sdd: 5860533168s Sector size (logical/physical): 512B/4096B Partition Table: gpt Disk Flags: Number Start End Size File system Name Flags 1 2048s 5860533134s 5860531087s ext4 primary Model: ATA ST3000DM001-1CH1 (scsi) Disk /dev/sde: 5860533168s Sector size (logical/physical): 512B/4096B Partition Table: gpt Disk Flags: Number Start End Size File system Name Flags 1 2048s 5860533134s 5860531087s primary Model: ATA ST3000DM001-1CH1 (scsi) Disk /dev/sdf: 5860533168s Sector size (logical/physical): 512B/4096B Partition Table: gpt Disk Flags: Number Start End Size File system Name Flags 1 2048s 5860533134s 5860531087s primary Model: Linux Software RAID Array (md) Disk /dev/md127: 17581584384s Sector size (logical/physical): 512B/4096B Partition Table: loop Disk Flags: Number Start End Size File system Flags 1 0s 17581584383s 17581584384s xfs =================================== == RAID 6 partitions information == =================================== Model: ATA TOSHIBA DT01ACA3 (scsi) Disk /dev/sdb: 5860533168s Sector size (logical/physical): 512B/4096B Partition Table: gpt Disk Flags: Number Start End Size File system Name Flags 1 2048s 5860533134s 5860531087s primary Model: ATA TOSHIBA DT01ACA3 (scsi) Disk /dev/sdc: 5860533168s Sector size (logical/physical): 512B/4096B Partition Table: gpt Disk Flags: Number Start End Size File system Name Flags 1 2048s 5860533134s 5860531087s primary Model: ATA TOSHIBA DT01ACA3 (scsi) Disk /dev/sdd: 5860533168s Sector size (logical/physical): 512B/4096B Partition Table: gpt Disk Flags: Number Start End Size File system Name Flags 1 2048s 5860533134s 5860531087s primary Model: ATA TOSHIBA DT01ACA3 (scsi) Disk /dev/sde: 5860533168s Sector size (logical/physical): 512B/4096B Partition Table: gpt Disk Flags: Number Start End Size File system Name Flags 1 2048s 5860533134s 5860531087s primary Model: ATA TOSHIBA DT01ACA3 (scsi) Disk /dev/sdf: 5860533168s Sector size (logical/physical): 512B/4096B Partition Table: gpt Disk Flags: Number Start End Size File system Name Flags 1 2048s 5860533134s 5860531087s primary Model: Linux Software RAID Array (md) Disk /dev/md127: 17580804096s Sector size (logical/physical): 512B/4096B Partition Table: loop Disk Flags: Number Start End Size File system Flags 1 0s 17580804095s 17580804096s xfsÿôèº{.nÇ+?·?®??+%?Ëÿ±éݶ¥?wÿº{.nÇ+?·¥?{±þ¶¢wø§¶?¡Ü¨}©?²Æ zÚ&j:+v?¨þø ¯ù ®w¥þ?à2?Þ?¨èÚ&¢)ß¡«a¶Úÿÿûàz¿äz¹Þ?ú+?ù???Ý¢jÿ?wèþf
