Thread: RAID 5 missing storage?

hello guys,

little bit confused , wondering if guys shed light on issue or if have set raid 5 incorrectly.

set raid 5 using 4 hard drives ( had old hdd's laying around decided create raid , setup ftp server house) , installed ubuntu 12.04 lts server edition last night.

harddrive sizes:
sda - 60gb
sdb - 80gb
sdc - 30gb
sdd - 40gb

thought creating raid array around 180gb - 190gb since loose storage swap space , parity bits.

however, after finished doing listed under ubuntu advance installation (raid) noticed raid 5 (/dev/md1) showed having 83.3gb of space?

used 3gb of space every hard drive swap space.
/dev/md0 has correct amount of space - 9gb swap:

sudo mdadm -d /dev/md0
/dev/md0:
version : 1.2
creation time : wed aug 15 23:06:07 2012
raid level : raid5
array size : 8781312 (8.37 gib 8.99 gb)
used dev size : 2927104 (2.79 gib 3.00 gb)
raid devices : 4
total devices : 4
persistence : superblock persistent

update time : wed aug 15 23:46:57 2012
state : clean
active devices : 4
working devices : 4
failed devices : 0
spare devices : 0

layout : left-symmetric
chunk size : 512k

name : ubuntu-srvr:0 (local host ubuntu-srvr)
uuid : 6f1c292f:7343a649:60a73f26:90ae9b22
events : 19

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


however, /dev/md1 ext4 filesystem shows has 83.3 gb??

sudo mdadm -d /dev/md1
/dev/md1:
version : 1.2
creation time : wed aug 15 23:06:38 2012
raid level : raid5
array size : 81317376 (77.55 gib 83.27 gb)
used dev size : 27105792 (25.85 gib 27.76 gb)
raid devices : 4
total devices : 4
persistence : superblock persistent

update time : thu aug 16 13:40:49 2012
state : clean
active devices : 4
working devices : 4
failed devices : 0
spare devices : 0

layout : left-symmetric
chunk size : 512k

name : ubuntu-srvr:1 (local host ubuntu-srvr)
uuid : 14d76d51:1deb54ec:d9dc43c2:19e659d3
events : 22

number major minor raiddevice state
0 8 2 0 active sync /dev/sda2
1 8 18 1 active sync /dev/sdb2
2 8 34 2 active sync /dev/sdc2
3 8 50 3 active sync /dev/sdd2


these disks used:

sudo fdisk -l

disk /dev/sda: 60.0 gb, 60022480896 bytes
255 heads, 63 sectors/track, 7297 cylinders, total 117231408 sectors
units = sectors of 1 * 512 = 512 bytes
sector size (logical/physical): 512 bytes / 512 bytes
i/o size (minimum/optimal): 512 bytes / 512 bytes
disk identifier: 0x000bbd1f

device boot start end blocks id system
/dev/sda1 2048 5859327 2928640 fd linux raid autodetect
/dev/sda2 * 5859328 117229567 55685120 fd linux raid autodetect

disk /dev/sdb: 80.0 gb, 80026361856 bytes
255 heads, 63 sectors/track, 9729 cylinders, total 156301488 sectors
units = sectors of 1 * 512 = 512 bytes
sector size (logical/physical): 512 bytes / 512 bytes
i/o size (minimum/optimal): 512 bytes / 512 bytes
disk identifier: 0x000167eb

device boot start end blocks id system
/dev/sdb1 2048 5859327 2928640 fd linux raid autodetect
/dev/sdb2 * 5859328 156301311 75220992 fd linux raid autodetect

disk /dev/sdc: 30.8 gb, 30758289408 bytes
255 heads, 63 sectors/track, 3739 cylinders, total 60074784 sectors
units = sectors of 1 * 512 = 512 bytes
sector size (logical/physical): 512 bytes / 512 bytes
i/o size (minimum/optimal): 512 bytes / 512 bytes
disk identifier: 0x0006e84d

device boot start end blocks id system
/dev/sdc1 2048 5859327 2928640 fd linux raid autodetect
/dev/sdc2 * 5859328 60073983 27107328 fd linux raid autodetect

disk /dev/sdd: 40.0 gb, 40020664320 bytes
255 heads, 63 sectors/track, 4865 cylinders, total 78165360 sectors
units = sectors of 1 * 512 = 512 bytes
sector size (logical/physical): 512 bytes / 512 bytes
i/o size (minimum/optimal): 512 bytes / 512 bytes
disk identifier: 0x000eece1

device boot start end blocks id system
/dev/sdd1 2048 5859327 2928640 fd linux raid autodetect
/dev/sdd2 * 5859328 78163967 36152320 fd linux raid autodetect

disk /dev/md1: 83.3 gb, 83268993024 bytes
2 heads, 4 sectors/track, 20329344 cylinders, total 162634752 sectors
units = sectors of 1 * 512 = 512 bytes
sector size (logical/physical): 512 bytes / 512 bytes
i/o size (minimum/optimal): 524288 bytes / 1572864 bytes
disk identifier: 0x00000000

disk /dev/md1 doesn't contain valid partition table

disk /dev/md0: 8992 mb, 8992063488 bytes
2 heads, 4 sectors/track, 2195328 cylinders, total 17562624 sectors
units = sectors of 1 * 512 = 512 bytes
sector size (logical/physical): 512 bytes / 512 bytes
i/o size (minimum/optimal): 524288 bytes / 1572864 bytes
disk identifier: 0x00000000

disk /dev/md0 doesn't contain valid partition table

disk /dev/sde: 4009 mb, 4009754624 bytes
124 heads, 62 sectors/track, 1018 cylinders, total 7831552 sectors
units = sectors of 1 * 512 = 512 bytes
sector size (logical/physical): 512 bytes / 512 bytes
i/o size (minimum/optimal): 512 bytes / 512 bytes
disk identifier: 0x00036ce1

device boot start end blocks id system
/dev/sde1 * 62 7826383 3913161 c w95 fat32 (lba)


normal loose space when creating raid 5 devices or did create raid incorrectly?

please advice.


in advance.

if i'm not mistaken, raid uses disks/partitions maximum size smallest of them. since /dev/sdc 30gb, array same if created 4 x 30gb disks.

raid5 loses 1 disk parity, have usable 3 x 30gb = 90gb. so, md1 of approx 83gb sounds right.

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